Cisco Bcmsn

Front 1

Layer 2 switching uses what value to forward data?

Back 1

MAC address

Front 2

Multilayer switching (MLS) forwards packets based on what OSI layers?

Back 2

Layers 2,3 and 4

Front 3

What does the 20/80 rule of networking state?

Back 3

Twenty percent of the traffic on a network segment stays local, while 80 percent of it
travels across the network.

Front 4

Where does a collision domain exist in a switched network?

Back 4

On a single switch port

Front 5

Where does a broadcast domain exist in a switched network?

Back 5

On a single VLAN

Front 6

What is a VLAN primarily used for?

Back 6

To segment a broadcast domain

Front 7

In which OSI layer should devices in the distribution layer typically operate?

Back 7

Layer 3

Front 8

How many layers are recommended in the hierarchical campus network design model?

Back 8

3

Front 9

A hierarchical network’s distribution layer aggregates which of the following?

Back 9

Access layer switches

Front 10

What might make a Catalyst 2950 a good choice for use in a wiring closet?

Back 10

high density of 10/100 ports

Front 11

In Multilayer switching, what hardware/software provides the Layer 3 routing function?

Back 11

Cisco Express Forwarding (CEF)

Front 12

Traffic destined for a specific set or group of users, regardless of their location on the campus network
is called what?

Back 12

Multicast traffic

Front 13

The new model of campus traffic has become known as what?

Back 13

The 20/80 rule

Front 14

Which Hierarchical Network Design layer includes devices with low cost per switch port,
high port density, scalable uplinks to higher layers,
user access functions such as VLAN membership, traffic and protocol filtering?

Back 14

Access layer

Front 15

Which Hierarchical Network Design layer includes High Layer 3 throughput for packet handling, Security and policy-based connectivity functions through access lists or packet filters, QoS features,
and Scalable and resilient high-speed links to the core and access layers?

Back 15

Distribution Layer

Front 16

Which Hierarchical Network Design layer includes Very high throughput at Layer 2 or Layer 3, No costly or unnecessary packet manipulations (access lists, packet filtering), Redundancy and resilience for high availability and Advanced QoS functions?

Back 16

core layer

Front 17

What is the purpose of breaking a campus network down into a hierarchical design?

Back 17

To make the network predictable and scalable

Front 18

What are the components of a typical switch block?

Back 18

access layer and distribution layer switches

Front 19

What are two types of core, or backbone, designs?

Back 19

Dual core and collapsed core

Front 20

In a properly designed hierarchical network, a broadcast from one PC will be confined to what?

Back 20

One switch block

Front 21

What is the maximum number of access layer switches that can connect into a single
distribution layer switch?

Back 21

Limited only by the number of ports on the distribution switch

Front 22

A switch block should be sized according to what two details?

Back 22

A study of the traffic patterns and flows and the number of access layer users

Front 23

How many distribution switches should be built into each switch block?

Back 23

2

Front 24

You can divide enterprise campus networks into what two basic elements?

Back 24

Switch block and Core block

Front 25

A group of access layer switches together with their distribution switches is called what?

Back 25

A switch block

Front 26

A group of enterprise servers along with their access and distribution (layer) switches is called what?

Back 26

Server Farm block

Front 27

A group of network management resources along with their access and distribution switches is called what?

Back 27

Management block

Front 28

A collection of services related to external network access, along with their access and distribution switches is called what?

Back 28

Enterprise Edge block

Front 29

The external network services contracted or used by the
enterprise network; these are the services with which the enterprise edge block interfaces. What is this called?

Back 29

Service Provider Edge block

Front 30

What type of core block is one where the hierarchy’s core layer is combined into the distribution layer?

Back 30

Collapsed core block

Front 31

In what type of core block are the distribution and core layers separate?

Back 31

Dual core block

Front 32

What device performs transparent bridging?

Back 32

Layer 2 switch

Front 33

When a PC is connected to a Layer 2 switch port, how far does the collision domain spread?

Back 33

1 switch port

Front 34

What information is used to forward frames in a Layer 2 switch?

Back 34

destination MAC address

Front 35

What does a switch do if a MAC address can’t be found in the CAM table?

Back 35

The switch floods the frame out all ports (except the receiving port).

Front 36

In the Catalyst 6500, frames can be filtered with access lists for security and QoS purposes. This filtering occurs at the same time as what?

Back 36

Simultaneously with a CAM table lookup

Front 37

In a switch, access list contents are compiled and merged into what?

Back 37

The TCAM table

Front 38

Multilayer switches using CEF are based on what switching technique?

Back 38

Topology-based switching

Front 39

In a switch, frames are placed in which buffer after forwarding decisions are made?

Back 39

Egress queue

Front 40

What size are the mask and pattern fields in a TCAM entry?

Back 40

134 bits

Front 41

Access list rules are compiled as TCAM entries. When a packet is matched against an access list, in what order are the TCAM entries evaluated?

Back 41

All entries are evaluated in parallel.

Front 42

Which Catalyst 3550 command can you use to display the addresses in the CAM table?

Back 42

show mac address-table

Front 43

CEF builds Layer 3 destination information from routing tables and Layer 2 data. Where is this information stored?

Back 43

This information is stored in hardware as a Forwarding Information Base (FIB) table.

Front 44

Multilayer switches can make many policy decisions in parallel using what?

Back 44

The Ternary Content
Addressable Memory (TCAM) contents.

Front 45

In a CEF switch, access lists for security (traditional router ACLs and VLAN ACLs) and QoS ACLs are compiled or merged into what?

Back 45

TCAM entries. These access lists can then be processed on each packet that passes through the switch, as a single table lookup.

Front 46

As a packet exits a multilayer switch, it must be rewritten so that its header and checksum values are valid. The fields in the original packet that the switch updates are what?

Back 46

— Source MAC address becomes the Layer 3 switch MAC address.
— Destination MAC address becomes the next-hop MAC address.
— IP TTL value is decremented by one.
— IP checksum is recomputed.
— Ethernet frame checksum is recomputed.

Front 47

What command is used to set the CAM table aging time?

Back 47

mac address-table aging-time [seconds]

Front 48

What command is used to configure a static CAM entry?

Back 48

mac address-table static [mac-address] vlan [vlan-id] interface [type mod/num]

Front 49

What command is used to clear a CAM table entry.

Back 49

clear mac address-table dynamic

Front 50

What command is used to set privileged level password to level 15?

Back 50

enable password level 15 [password]

Front 51

What command is used to view the CAM table?

Back 51

show mac address-table dynamic

Front 52

What command is used to view the CAM table size?

Back 52

show mac address-table count

Front 53

What command is used to view TCAM resource information?

Back 53

show tcam counts

Front 54

By default, how long are CAM table entries kept before they are aged out?

Back 54

300 seconds

Front 55

A TCAM lookup involves which 3 values?

Back 55

mask, value and result

Front 56

How many table lookups are required to find a MAC address in the CAM table?

Back 56

1

Front 57

How many table lookups are required to match a packet against an access list that has been compiled into 10 TCAM entries?

Back 57

1

Front 58

How many value patterns can a TCAM store for each mask?

Back 58

8

Front 59

Can all packets be switched in hardware by a multilayer switch?

Back 59

No; some must be flagged for process switching by the switch CPU.

Front 60

Multilayer switches must rewrite which 3 portions of an Ethernet frame?

Back 60

Source and destination MAC addresses
IP time-to-live
Checksums

Front 61

If a station only receives Ethernet frames and doesn’t transmit anything, how will a switch learn of its location?

Back 61

You must configure a static CAM entry with the station’s MAC address and the switch port
where it is located. Otherwise, the switch must flood each and every frame destined for that host
out every switch port in an effort to find it.

Front 62

What is a TCAM’s main purpose?

Back 62

To process access lists as a single table lookup

Front 63

Why do the TCAM mask and pattern fields consist of so many bits?

Back 63

So that a combination of several address fields in a frame can be inspected at once

Front 64

In a multilayer switch with a TCAM, a longer access list (more ACEs or statements) takes longer to process for each frame. True or false?

Back 64

False

Front 65

A multilayer switch receives a packet with a certain destination IP address. Suppose the switch
has that IP address in its Layer 3 forwarding table, but no corresponding Layer 2 address. What vhappens to the packet next?

Back 65

The switch CPU sends an ARP request.

Front 66

If a multilayer switch can’t support a protocol with CEF, it relies on fallback bridging. Can the switch still route that traffic?

Back 66

No. That traffic is transparently bridged. An external multilayer switch or router is required to take the bridged packets and route them.

Front 67

To configure a static CAM table entry, the mac address-table static mac-address command is used. Which two other parameters must also be given?

Back 67

vlan [vlan-id]
interface [type mod/num]

Front 68

What portion of the TCAM is used to evaluate port number comparisons in an access list?

Back 68

LOU

Front 69

Someone has asked you where the host with MAC address 00-10-20-30-40-50 is located.
Assuming you already know the switch it is connected to, what command can you use to find it?

Back 69

show mac address-table dynamic address 0010.2030.4050

Front 70

What protocol is used to advertise CAM table entries among neighboring switches?

Back 70

None; the entries are not advertised.

Front 71

When a frame arrives at a switch port where is it placed?

Back 71

In the ingress queue

Front 72

In a switch, the Layer 2 forwarding table is called what?

Back 72

CAM table

Front 73

Catalyst switches support what two basic generations or types of MLS?

Back 73

route caching and topology based

Front 74

Where does Cisco Express Forwarding (CEF) download the current routing table database?

Back 74

into the Forwarding
Information Base (FIB)

Front 75

What is the L3 Forwarding Table in a switch called?

Back 75

The FIB table

Front 76

All Catalyst switch models use what table for Layer 2 switching?

Back 76

a Content Addressable Memory (CAM)

Front 77

By default, idle CAM table entries are kept for 300 seconds before they are deleted. You can change the default setting using what command?

Back 77

mac address-table aging-time [seconds]

Front 78

After an access list has been created or configured, what software compiles, or merges, the ACEs into entries in the TCAM table?

Back 78

Feature Manager software

Front 79

What software configures or tunes the TCAM partitions,
if needed?

Back 79

The SDM software

Front 80

TCAM entries are composed of what combinations?

Back 80

Value, Mask, and Result (VMR)

Front 81

What is the name for the operating system available on Cisco Catalyst 3550, 4500, and
6500 family switches?

Back 81

Cisco IOS

Front 82

Which user interface mode allows the greatest authority for making configuration changes?

Back 82

Privileged EXEC (enable) mode

Front 83

To configure a password for Telnet access to a switch, what must the password be applied to?

Back 83

line vty 0 15

Front 84

Which protocol is used to exchange information between connected Cisco neighbors?

Back 84

CDP

Front 85

Cisco Discovery Protocol is sent over which OSI layer?

Back 85

Layer 2

Front 86

Which Catalyst file system contains the running IOS software image?

Back 86

Flash

Front 87

Which command saves newly made configuration changes so they will be automatically used after the next switch reload?

Back 87

copy running-config startup-config

Front 88

What command can you use to view information received from a neighboring Cisco switch, including its version of IOS?

Back 88

show cdp neighbors detail

Front 89

What command is used to set the privileged level password?

Back 89

enable secret [password]

Front 90

What command is used to copy a file between Flash and a TFTP server?

Back 90

copy flash:[filename] tftp:

Front 91

What command is used to clear Flash contents?

Back 91

erase flash:
-OR-
format flash:

Front 92

What command is used to save the running configuration?

Back 92

copy running-config startup-config

Front 93

What command is used to display the current running environment and IOS version?

Back 93

show version

Front 94

What command is used to display the running configuration?

Back 94

show running-config

Front 95

What command is used to display the permanent configuration?

Back 95

show startup-config
-OR-
show config

Front 96

What command is used to display all technical support information?

Back 96

show tech-support

Front 97

How often are CDP announcements sent?

Back 97

Every 60 seconds

Front 98

What command can you use to verify CDP configuration on switch port GigabitEthernet 3/1?

Back 98

shop cdp interface gi 3/1

Front 99

What mode are you in with the following command line prompt:
Switch#

Back 99

Privileged EXEC or enable mode

Front 100

What mode are you in with the following command line prompt:
Switch(config)#

Back 100

Global configuration mode

Front 101

What mode are you in with the following command line prompt:
Switch(config-if)#

Back 101

Interface configuraion mode

Front 102

What mode are you in with the following command line prompt:
Switch>

Back 102

Normal user EXEC mode

Front 103

To change the host or system name, you enter what command in configuration mode?

Back 103

Switch(config)# hostname [hostname]

Front 104

By default, a switch allows user access only via what?

Back 104

the console port

Front 105

CDP frames are sent as multicasts, using a
destination MAC address of what?

Back 105

01:00:0c:cc:cc:cc

Front 106

To manually enable CDP on an
interface, you use what interface configuration command?

Back 106

Switch(config-if)# [no] cdp enable

Front 107

What is the nonvolatile memory present in the switch? Files stored here remain intact even after a power cycle.

Back 107

Flash

Front 108

Nonvolatile memory that contains the switch configuration used during bootup is called what?

Back 108

NVRAM

Front 109

What does the IEEE 802.3 standard define?

Back 109

Ethernet

Front 110

At what layer are traditional 10 Mbps Ethernet, Fast Ethernet, and Gigabit Ethernet the same?

Back 110

Layer 2

Front 111

At what layer are traditional 10 Mbps Ethernet, Fast Ethernet, and Gigabit Ethernet different?

Back 111

Layer 1

Front 112

What is the maximum cable distance for a Category 5 100BASE-TX connection?

Back 112

100 meters

Front 113

Where is Cisco Long Reach Ethernet typically used?

Back 113

In a multitenant building

Front 114

What is the maximum length of a Cisco LRE connection?

Back 114

5000 feet

Front 115

Ethernet autonegotiation determines which of the following?

Back 115

duplex mode

Front 116

What cannot be determined by an ethernet port if the far end of a connection doesn’t support autonegotiation?

Back 116

duplex

Front 117

What type of cable should you use to connect two switches back-to-back using their
FastEthernet 10/100 ports?

Back 117

Crossover cable

Front 118

If a switch port is in the “errdisable” state, what is the first thing you should do?

Back 118

Determine the cause of the problem.

Front 119

What is the IEEE name for fast ethernet?

Back 119

802.3u

Front 120

What is the IEEE name for gigabit ethernet on fiber?

Back 120

802.3z

Front 121

What is the IEEE name for gigabit ethernet on copper?

Back 121

802.3ab

Front 122

What is the IEEE name for 10 gigabit ethernet?

Back 122

802.3ae

Front 123

What command is used to select multiple switch ports for configuration?

Back 123

interface
range [type module/first-number – last-number]

Front 124

What command is used to give a name to a port?

Back 124

description [description-string]

Front 125

What command is used to set port speed?

Back 125

speed [10 | 100 | 1000 | auto]

Front 126

What command is used to set port mode?

Back 126

duplex [auto | full | half]

Front 127

When a 10/100 Ethernet link is autonegotiating, which will be chosen if both stations can
support the same capabilities—10BASE-T full duplex, 100BASE-TX half duplex, or
100BASE-TX full duplex?

Back 127

100BASE-TX full duplex will be chosen because it has the highest autonegotiation priority and is common to both end stations.

Front 128

How many pairs of copper wires does a 1000BASET connection need?

Back 128

4 pairs

Front 129

Which GBIC would you use for a connection over multimode fiber (MMF)?

Back 129

You could use either a 1000BASE-SX or a 1000BASE-LX/LH.

Front 130

A Category 5 cable having only pins 1,2 and 3,6 has been installed and used for a Fast Ethernet
link. Can this same cable be used for a migration to Gigabit Ethernet using 1000BASE-T GBICs, assuming the length is less than 100 meters?

Back 130

No. 1000BASE-T requires all four pairs of wires to be present.

Front 131

What types of Ethernet are commonly used to connect geographically separate locations?

Back 131

Metro Ethernet, transported over facilities contracted from a service provider

Front 132

What form of Metro Ethernet allows several enterprise VLANs to be transported between locations—TLS or DVS?

Back 132

Directed VLAN Service (DVS)

Front 133

What one switch command will select Fast Ethernet interfaces 4/1 through 48 for a common configuration?

Back 133

interface range fastethernet 4/1 - 48 (Don’t forget spaces around the dash.)

Front 134

What command can you use to make sure that no switch ports are automatically shut down in an errdisable state for any reason?

Back 134

no errdisable detect cause all

Front 135

In which Metro Ethernet deployment are all of a customer’s connected sites appear as a single common VLAN (broadcast domain)?

Back 135

Transparent LAN Service (TLS)

Front 136

In which Metro Ethernet deployment can a customer’s VLANs be connected wherever they exist, rather than everywhere. This allows one VLAN to be connected between two sites while another VLAN connects to two other sites, and so on. A customer is allowed to have multiple
VLANs transported by the service provider network.

Back 136

Directed VLAN Service (DVS)

Front 137

In what technology does A single fiber connection transports many different Gigabit Ethernet datastreams by placing each within a
different wavelength (represented by the Greek letter lambda λ) of light?

Back 137

Dense Wave Division Multiplexing (DWDM)

Front 138

In what technology does A single fiber connection transports up to 8 different Gigabit Ethernet datastreams by placing each within a
different wavelength (represented by the Greek letter lambda λ) of light?

Back 138

Coarse Wave Division Multiplexing (CWDM)

Front 139

Catalyst switch families use what to make the console connection between a PC (or terminal or modem) and the console port.

Back 139

an RJ-45-to-RJ-45 rollover cable

Front 140

What GBIC provides short wavelength connectivity using SC fiber connectors and MMF
for distances up to 550 meters (1804 feet)?

Back 140

1000BASE-SX GBIC

Front 141

What GBIC provides long wavelength/long haul connectivity using SC fiber connectors and either MMF or single-mode fiber (SMF)?

Back 141

1000BASE-LX/LH GBIC

Front 142

What GBIC provides GBIC—extended distance connectivity using SC fiber connectors and SMF; works for distances up to 70 km, and even to 100 km when used with premium grade SMF?

Back 142

1000BASE-ZX GBIC

Front 143

What GBIC uses a proprietary connector with a high-data-rate copper cable with
enhanced signal integrity and electromagnetic interference (EMI) performance to provides a GBIC-to-GBIC connection between stacking Catalyst switches or between any two Gigabit switch ports over a short distance?

Back 143

GigaStack GBIC

Front 144

What GBIC provides an RJ-45 connector for 4-pair UTP cabling; works for distances
up to 100 m (328 feet?

Back 144

1000BASE-T GBIC

Front 145

A 10-Mbps Ethernet link (fixed speed) defaults to what duplex?

Back 145

half duplex

Front 146

A 100-Mbps Fast Ethernet (dual speed 10/100) link defaults to what duplex?

Back 146

full duplex

Front 147

What Cisco switch feature detects when a Spanning Tree bridge protocol data unit (BPDU) is received on
a port configured for STP portfast?

Back 147

bpduguard

Front 148

What command is used to enable and use a switch port?

Back 148

no shutdown

Front 149

A VLAN is what kind of domain?

Back 149

A broadcast domain

Front 150

Switches provide VLAN connectivity at which layer of the OSI model?

Back 150

Layer 2

Front 151

What is needed to pass data between two PCs, each connected to a different VLAN?

Back 151

A Layer 3 process on a switch or router

Front 152

Which switch command is used to assign a port to a VLAN?

Back 152

switchport access vlan [vlan-id]

Front 153

What is the Cisco proprietary method for trunk encapsulation?

Back 153

ISL

Front 154

Which protocol dynamically negotiates trunking parameters?

Back 154

DTP - Dynamic Trunking Protocol

Front 155

How many different VLANs can an 802.1Q trunk support?

Back 155

4,096

Front 156

If two switches each support all types of trunk encapsulation on a link between them, which
one will be negotiated?

Back 156

ISL

Front 157

What is the purpose of an 802.1Q tunnel?

Back 157

To transport an 802.1Q trunk across a service provider network

Front 158

Which VLAN trunk encapsulation method adds a 26-byte header, a 4-byte trailer to each frame, and includes a 10-bit VLAN ID?

Back 158

ISL

Front 159

Which VLAN trunk encapsulation method adds a 4-byte tag; includes a 12-bit VLAN ID

Back 159

802.1Q

Front 160

What two commands create a VLAN and name it?

Back 160

vlan [vlan-num]
name [vlan-name]

Front 161

What three commands assign a port to a VLAN?

Back 161

interface [type module/number]
switchport mode access
switchport access vlan [vlan-num]

Front 162

What command is used to verify VLAN configuration?

Back 162

show vlan id [vlan-id]

Front 163

What command is used to verify active trunk parameters?

Back 163

show interface [type mod/num]trunk

Front 164

What command is used to verify DTP operation?

Back 164

show dtp [interface type mod/num]

Front 165

Name two types of VLANs in terms of spanning areas of the campus network.

Back 165

Local VLAN
End-to-end VLAN

Front 166

What three switch commands would configure Fast Ethernet port 4/11 for VLAN 2?

Back 166

interface fastethernet 4/11
switchport mode access
switchport access vlan 2

Front 167

What is the default VLAN on all ports of a Catalyst switch?

Back 167

VLAN 1

Front 168

What methods of Ethernet VLAN frame identification can be used on a Catalyst switch trunk?

Back 168

802.1Q
ISL

Front 169

What is the difference between the two VLAN trunking methods? How many bytes are added to trunked frames for VLAN identification in each method?

Back 169

ISL uses encapsulation and adds a 26-byte header and a 4-byte trailer. 802.1Q adds a
4-byte tag field within existing frames, without encapsulation.

Front 170

What is the purpose of Dynamic Trunking Protocol (DTP)?

Back 170

DTP allows negotiation of a common trunking method between endpoints of a trunk link.

Front 171

What commands are needed to configure a Catalyst switch trunk port Gigabit 3/1 to transport only VLANs 100, 200 through 205, and 300 using IEEE 802.1Q?

Back 171

switchport trunk allowed vlan 100, 200-205, 300

Front 172

Two neighboring switch trunk ports are set to the auto mode with ISL trunking encapsulation mode. What will the resulting trunk mode become?

Back 172

Trunking will not be established at all. Both switches are in the passive auto state and are waiting to be asked to start the trunking mode. The link will remain an access link on both switches.

Front 173

What is the command to configure the switch port to use DTP to actively ask the other end to become a trunk?

Back 173

switchport mode dynamic desirable

Front 174

Which command can set the native VLAN of a trunk port to VLAN 100 after the interface has been selected?

Back 174

switchport trunk native vlan 100

Front 175

What command can configure a trunk port to stop sending and receiving DTP packets
completely?

Back 175

switchport nonegotiate

Front 176

What command can be used on a Catalyst switch to verify exactly what VLANs will be
transported over trunk link gigabitethernet 4/4?

Back 176

show interface gigabitethernet 4/4 switchport
-OR-
show interface gigabitethernet 4/4 trunk

Front 177

What type of switch port must a customer present to a service provider if an IEEE 802.1Q tunnel is desired?

Back 177

802.1Q trunk

Front 178

A full Layer 2-only switched network is referred to as what?

Back 178

a flat network topology.

Front 179

What are the two VLAN membership methods exist on Cisco Catalyst switches?

Back 179

static and dynamic

Front 180

Which VLAN membership methods is port based?

Back 180

static VLAN membership

Front 181

What is the name of the VLAN database where VLAN information is automatically stored on a switch?

Back 181

vlan.dat

Front 182

What 3 commands are used to assign switc ports to VLANs?

Back 182

Switch(config)# interface [type module/number]
Switch(config-if)# switchport mode access
Switch(config-if)# switchport access vlan [vlan-num]

Front 183

What command outputs a list of all VLANs defined in the switch?

Back 183

show vlan

Front 184

What type of VLAN spans the entire switch fabric of a network?

Back 184

end to end VLAN

Front 185

Cisco supports trunking on what type of switch links?

Back 185

Cisco supports trunking on both Fast Ethernet and Gigabit Ethernet switch links

Front 186

VLAN identification can be performed using what two methods?

Back 186

Inter-Switch Link (ISL) protocol and IEEE 802.1Q protocol

Front 187

Which VLAN trunking method imbeds information into the frame?

Back 187

802.1Q

Front 188

How does ISL modify a frame?

Back 188

ISL adds a 26-byte header and
a 4-byte trailer to the frame.

Front 189

How many bytes does ISL add to each frame?

Back 189

ISL adds a total of 30 bytes to each frame

Front 190

How many bytes does 802.1Q add to each frame?

Back 190

802.1Q adds 4 bytes

Front 191

Can a router participate in the DTP negotiation protocol?

Back 191

No

Front 192

Are switch ports enabled for trunking by default?

Back 192

No, by default, all switch ports are non-trunking

Front 193

What 5 commands are needed to set up a port as a trunk link?

Back 193

interface [type mod/port]
switchport trunk encapsulation [isl | dot1q | negotiate]
switchport trunk native vlan [vlan-id]
switchport trunk allowed vlan [vlan-list | all |
add | except | remove] vlan-list
switchport mode [trunk | dynamic {desirable | auto}}

Front 194

Which command defines which VLANs can be trunked over the
link?

Back 194

switchport trunk allowed vlan

Front 195

Which VLAN is the Cisco default, which carries control protocols such as CDP, VTP, and STP

Back 195

VLAN 1

Front 196

Which setting places a port in permanent trunking mode?

Back 196

switchport mode trunk -
The port at the other end of the trunk should be similarly configured because negotiation is not
allowed. You should also manually configure the encapsulation mode.

Front 197

Which switchport mode is the default for trunking?

Back 197

dynamic desirable

Front 198

In which switchport mode does the port actively attempts to convert the link into trunking
mode?

Back 198

dynamic desirable -
If the far-end switch port is configured to trunk, dynamic desirable, or dynamic auto
mode, trunking is successfully negotiated.

Front 199

In which switchport mode does the port convert the link into trunking mode?

Back 199

switchport mode dynamic auto - If the far-end switch port is
configured to trunk or dynamic desirable, trunking is negotiated. Because of the passive negotiation behavior, the link never becomes a trunk if both ends of the link are left to the dynamic auto default.

Front 200

How often are DTP frames rent out?

Back 200

DTP frames are sent out every 30 seconds

Front 201

What command disables DTP completely so that DTP frames are not exchanged?

Back 201

switchport nonegotiate

Front 202

what technique allows trunk tunneling to be accomplished across a service provider’s core network without 802.1Q
trunks?

Back 202

Ethernet over MPLS (EoMPLS)

Front 203

What command puts a switch port into the tunnel mode?

Back 203

switchport mode dot1qtunnel

Front 204

What command is used o verify a VLAN’s configuration on a switch?

Back 204

show vlan id [vlan]

Front 205

Which VTP modes does not allow any manual VLAN configuration changes?

Back 205

client mode

Front 206

How many VTP management domains can a Catalyst switch participate in?

Back 206

only 1

Front 207

Which command configures a Catalyst 3550 for VTP client mode?

Back 207

vtp mode client

Front 208

What is the purpose of VTP pruning?

Back 208

to limit the extent of broadcast traffic

Front 209

Which VLAN number is never eligible for VTP pruning?

Back 209

VLAN 1

Front 210

If a VTP server is configured for VTP version 2, what else must happen for successful VTP
communication in a domain?

Back 210

All other switches in the domain must be version 2 capable.

Front 211

What VTP modes can a Catalyst switch be configured for?

Back 211

Server, client, and transparent modes.

Front 212

Are VLANs advertised in VTP transparent mode?

Back 212

No

Front 213

Can VLANs be created in VTP transparent mode?

Back 213

Yes

Front 214

Can VLANs be created in VTP client mode?

Back 214

No

Front 215

How many VTP management domains can a Catalyst switch participate in?

Back 215

A switch can be a member of only one VTP management domain.

Front 216

On a VTP server switch, identify what you can do to reset the VTP configuration revision number to 0.

Back 216

Set the VTP domain name to a bogus value and change it back OR Configure the switch for VTP transparent mode and then configure the switch back to server mode.

Front 217

How can you clear the configuration revision number on a VTP client?

Back 217

You can’t. The VTP client bases all VLAN and VTP information on advertisements from a VTP
server. Therefore, the configuration revision number on the client comes directly from the same number on the server.

Front 218

What command would be used to make all VLANs other than 30 and 100 eligible for pruning on a trunk interface?

Back 218

switchport trunk pruning vlan except 30,100

Front 219

Which VLAN numbers are never eligible for VTP pruning?

Back 219

VLAN 1 and VLANs 1001 to 1005.

Front 220

What does the acronym VTP stand for?

Back 220

VLAN Trunking Protocol

Front 221

What VTP domain name is defined on a new switch with no configuration?

Back 221

A NULL or empty string. The switch defaults to server mode and will learn a VTP domain
name from the first VTP server heard on a trunk link. Otherwise, you must manually configure the domain name.

Front 222

What command will show information about the VTP configuration on a Catalyst 3550?

Back 222

show vtp status

Front 223

The VLAN Trunking Protocol (VTP)operates at what layer o the OSI model?

Back 223

Layer 2

Front 224

In how many VTP domains can a switch belong to?

Back 224

A switch can belong to only one VTP domain

Front 225

When a VLAN is added to a switch in a management
domain, other switches are notified of the new VLAN through what?

Back 225

a VTP advertisement

Front 226

By default, a switch is in what VTP mode?

Back 226

VTP server mode

Front 227

VTP advertisements are sent as what type of frame?

Back 227

multicast frames

Front 228

The VTP advertisement process starts with what configuration revision number?

Back 228

zero (0)

Front 229

Can a VTP revision number be
altered by a power cycle of the switch?

Back 229

No, it is stored in NVRAM and is not altered by a power cycle of the switch

Front 230

What are the three forms of VTP advertisements?

Back 230

Summary advertisements
Subset advertisements
Advertisement requests from clients

Front 231

When do VTP domain servers send summary advertisements?

Back 231

every 300 seconds and every time a VLAN database change occurs.

Front 232

For VLAN configuration changes, summary advertisements are followed
by what?

Back 232

one or more subset advertisements with more specific VLAN configuration data.

Front 233

When do VTP domain servers send subset advertisements?

Back 233

after a VLAN configuration change occurs.

Front 234

What global configuration command is used to assign a switch to a VTP management
domain?

Back 234

Switch(config)# vtp domain [domain-name]

Front 235

What command configures the VTP mode on a switch?

Back 235

Switch(config)# vtp mode [server | client | transparent]

Front 236

What is the default VTP protocol on a switch?

Back 236

VTP version 1 is the default protocol on a switch.

Front 237

The current VTP parameters for a management domain can be displayed with what command?

Back 237

show vtp status

Front 238

VTP message and error counters can be displayed with what command?

Back 238

show vtp counters

Front 239

VTP pruning makes more efficient use of trunk bandwidth by doing what?

Back 239

by reducing unnecessary flooded traffic (broadcasts and unknown unicasts)

Front 240

By default, is VTP pruning disabled or enabled on IOS-based switches?

Back 240

disabled

Front 241

To enable VTP pruning, use what global configuration command?

Back 241

Switch(config)# vtp pruning

Front 242

Does the the VTP password on one switch have to match others in the VTP domain?

Back 242

Yes

Front 243

If Fast Ethernet ports are bundled into an EtherChannel, what is the maximum throughput
supported on a Catalyst switch?

Back 243

1600 Mbps

Front 244

What type of interface represents an EtherChannel as a whole?

Back 244

Port-channel

Front 245

The EtherChannel load-balancing method can be set how?

Back 245

globally per switch

Front 246

What logical operation is performed to calculate EtherChannel load balancing as a function of two addresses?

Back 246

XOR

Front 247

When would PagP’s “desirable silent” mode be useful?

Back 247

When the switch should not expect to receive PAgP frames

Front 248

Which EtherChannel mode does not send or receive any negotiation frames?

Back 248

channel-group 1 mode on

Front 249

Which command can be used to see the status of an EtherChannel’s links?

Back 249

show etherchannel summary

Front 250

How many links can be aggregated into an EtherChannel?

Back 250

2-8

Front 251

What are the two main benefits of an EtherChannel?

Back 251

Increased bandwidth
Link redundancy

Front 252

Traffic between two hosts will be distributed across all links in an EtherChannel. True or false?

Back 252

False

Front 253

Which three methods can you use to distribute traffic in an EtherChannel?

Back 253

MAC address
IP address
Layer 4 port

Front 254

What protocols can negotiate an EtherChannel between two switches?

Back 254

PAgP
LACP

Front 255

Suppose a switch at one end of an EtherChannel is configured to use source MAC addresses for load balancing. The switch on the other end is configured to use both source and destination IP addresses. What will happen?

Back 255

The EtherChannel will successfully transport traffic between the two switches. However, the
traffic load will not be distributed evenly or symmetrically across the links in the channel.

Front 256

What does the acronym PAgP stand for?

Back 256

Port Aggregation Protocol

Front 257

Two switches should be configured to negotiate an EtherChannel. If one switch is using PAgP “auto” mode, what should the other switch use?

Back 257

PAgP “desirable” mode

Front 258

What interface configuration command is needed to select LACP as the EtherChannel
negotiation protocol?

Back 258

channel-protocol lacp

Front 259

What command could you use to see the status of every port in an EtherChannel?

Back 259

show etherchannel summary

Front 260

What command could you use to verify the hashing algorithm used for EtherChannel load
balancing?

Back 260

show etherchannel load-balance

Front 261

What five attributes of a set of switch ports must match to form an EtherChannel?

Back 261

Port speed
Port duplex
Trunking mode
Trunking encapsulation
Access or native VLAN

Front 262

What command would be used to select an EtherChannel load-balancing method for a switch?

Back 262

port-channel load-balance [method]

Front 263

What two commands would be used use a PAgP mode on an interface and set up an EtherChannel?

Back 263

channel-protocol pagp
channel-group [number] mode [on | auto |
desirable]

Front 264

What command is used to configure frame distribution
for all EtherChannel switch links?

Back 264

Switch(config)# port-channel load-balance [method]

Front 265

What commandis used to verify how effective a configured load-balancing method for EtherChannel is performing?

Back 265

The show etherchannel port-channel command. Each link in the channel will be displayed,
along with a “Load” value.

Front 266

What does LACP stand for?

Back 266

Link Aggregation Control Protocol (LACP), it is a standards-based method of creating an EtherChannel

Front 267

What EtherChannel mode does not send or receive PAgP or LACP packets?

Back 267

on mode

Front 268

What EtherChannel mode attempts to ask the far end to bring up a channel?

Back 268

EtherChannel desirable (PAgP) or active (LACP) mode attempts to ask the far end to bring up a channel. Therefore, the other end must be set to either desirable or auto mode.

Front 269

What EtherChannel mode mode participates in the channel protocol, but only if the far end asks for participation?

Back 269

EtherChannel auto (PAgP) or passive (LACP) mode participates in the channel protocol, but only if the far end asks for participation. Two switches in the auto or passive mode will not form an EtherChannel.

Front 270

What command is used to verify the EtherChannel state?

Back 270

show etherchannel summary

Front 271

What command is used to verify the EtherChannel channel negotiation mode?

Back 271

show etherchannel port

Front 272

What command is used to show detailed status about each EtherChannel component?

Back 272

show etherchannel detail

Front 273

How is a bridging loop best described?

Back 273

A loop formed between switches where frames circulate endlessly

Front 274

Configuration BPDUs are originated by what?

Back 274

Only the Root Bridge switch

Front 275

What is the single most important design decision to be made in a network running STP?

Back 275

Root Bridge placement

Front 276

What happens to a port that is neither a Root Port nor a Designated Port?

Back 276

It is put into the Blocking state.

Front 277

What is the maximum number of Root Ports that a Catalyst switch can have?

Back 277

1

Front 278

What mechanism is used to set STP timer values for all switches in a network?

Back 278

Configuring the timers on the Root Bridge switch.

Front 279

If a switch port is in this STP state, MAC addresses can be placed into the CAM table, but no data can be sent or received?

Back 279

Learning

Front 280

What is the default “hello” time for IEEE 802.1D?

Back 280

2 seconds

Front 281

If a switch has 10 VLANs defined and active, how many instances of STP will run using PVST+ versus CST?

Back 281

10 for PVST+, 1 for CST

Front 282

What are the five STP states?

Back 282

disabled, blocking, listening, learning, forwarding

Front 283

In what STP port state can a port receive BPDUs but cannot send or receive data or learn MAC addresses?

Back 283

blocking

Front 284

In what STP port state can a port send and receive BPDUs but cannot send or receive data or learn MAC addresses?

Back 284

Listening

Front 285

In what STP port state can a port send and receive BPDUs
and learn MAC addresses but cannot send or receive data?

Back 285

Learning

Front 286

In what STP port state can a port send and receive BPDUs,
learn MAC addresses, and
send and receive data?

Back 286

Forwarding

Front 287

In spanning tree, which bridge becomes the root bridge?

Back 287

Bridge with Lowest Bridge ID

Front 288

In spanning tree, which port becomes the root port?(one per switch)

Back 288

Port with the lowest Root Path Cost

Front 289

What is the STP port path cost for 4 Mbps?

Back 289

250

Front 290

What is the STP port path cost for 10 Mbps?

Back 290

100

Front 291

What is the STP port path cost for 16 Mbps?

Back 291

62

Front 292

What is the STP port path cost for 45 Mbps?

Back 292

39

Front 293

What is the STP port path cost for 100 Mbps?

Back 293

19

Front 294

What is the STP port path cost for 1 Gbps?

Back 294

4

Front 295

What is the STP port path cost for 10 Gbps?

Back 295

2

Front 296

What is the default value for STP forward delay?

Back 296

15 seconds

Front 297

What is the default value for STP max age?

Back 297

20 seconds

Front 298

What is the time spent in Listening and Learning states before transitioning
toward Forwarding state in STP called?

Back 298

forward delay (15 seconds)

Front 299

What is the maximum length of time a BPDU can be stored without receiving an update called?

Back 299

max age (20 seconds)

Front 300

What type of spanning tree has one instance of STP, over the native VLAN; 802.1Q-based?

Back 300

CST (common spanning tree)

Front 301

What type of spanning tree has one instance of STP per VLAN; Cisco ISL-based?

Back 301

PVST

Front 302

What type of spanning tree provides interoperability between CST and PVST; operates over both 802.1Q and ISL?

Back 302

PVST+

Front 303

What are two types of STP messages used to communicate between bridges?

Back 303

Configuration BPDU
ACK BPDU

Front 304

In STP, what criteria are used to select the Root Bridge?

Back 304

Lowest Bridge ID (Bridge priority, MAC address)

Front 305

In STP, what criteria are used to select the Root Port?

Back 305

Lowest Root Path Cost

Front 306

In STP, what criteria are used to select the Designated Port?

Back 306

Lowest Root Path Cost on a shared segment

Front 307

A Root Bridge has been elected in a switched network. Suppose a new switch is installed with a lower Bridge ID than the existing Root Bridge. What will happen?

Back 307

The new switch will begin life by advertising itself as the Root Bridge, thinking it is the only bridge on the network. Because it has a lower Bridge ID than the current Root, it will win the
election after the BPDUs converge and all switches have a knowledge of the new, better choice.

Front 308

Suppose a switch receives Configuration BPDUs on two of its ports. Both ports are assigned to the same VLAN. Each of the BPDUs announces Catalyst A as the Root Bridge. Can the switch use both of these ports as Root Ports? Why?

Back 308

The STP doesn’t allow more than one Root Port per switch (bridge). Because of this, both ports cannot become Root Ports. Only the port with the lowest Root Path Cost (or one of the successive STP tie-breaker decisions) will become the Root Port.

Front 309

What parameters can be tuned to influence the selection of a port as a Root or Designated Port?

Back 309

Port Cost

Front 310

Using the default STP timers, how long does it take for a port to move from the Blocking state to the Forwarding state?

Back 310

30 seconds

Front 311

Over what VLAN(s) does the CST form of STP run?

Back 311

The native VLAN

Front 312

What is the major difference between PVST and PVST+?

Back 312

PVST+ interoperates with CST and PVST.

Front 313

STP data messages are exchanged in the form of what?

Back 313

BPDUs (bridge protocol data units)

Front 314

BPDU frames have a destination address of what well-known STP multicast
address?

Back 314

01-80-c2-00-00-00

Front 315

What two types of BPDUs exist?

Back 315

Configuration BPDU, used for Spanning Tree computation and Topology Change Notification (TCN) BPDU, used to announce changes in the network
topology

Front 316

The Bridge ID is an 8-byte value consisting of
what fields?

Back 316

Bridge priority (2 bytes) and MAC address (8 bytes)

Front 317

On a switch running STP, the one port that has the best path to the Root Bridge is called what?

Back 317

The root port

Front 318

The time interval that a switch stores a BPDU before discarding it is called what?

Back 318

Max Age (20 seconds)

Front 319

Default STP timer values are based on what network diameter?

Back 319

7 switches

Front 320

In STP, to announce a change in the active network topology, switches send out what?

Back 320

TCN BPDUs (Topology Change Notification BPDUs)

Front 321

Where should the Root Bridge be placed on a network?

Back 321

Closest to the center of the network

Front 322

What can happen as a result of a poorly placed Root Bridge in a network?

Back 322

STP topology can take unexpected paths.

Front 323

What should you change to make a switch become a Root Bridge?

Back 323

Bridge Priority

Front 324

What is the default STP Bridge Priority on a Catalyst switch?

Back 324

32,768

Front 325

What command can make a switch become the Root Bridge for VLAN 5, assuming that all switches have the default STP parameters?

Back 325

spanning-tree vlan 5 priority 100
(something less than 32,768)

Front 326

What is the default Path Cost of a Gigabit Ethernet switch port?

Back 326

4

Front 327

What command can change the Path Cost of interface Gigabit Ethernet 3/1 to a value of 8?

Back 327

spanning-tree cost 8

Front 328

What happens if the Root Bridge switch and another switch are configured with different STP hello timer values?

Back 328

The other switch changes its hello timer to match the Root Bridge.

Front 329

What network diameter value is the basis for the default STP timer calculations?

Back 329

7

Front 330

Where should the STP PortFast feature be used?

Back 330

An access layer switch port connected to a PC

Front 331

Where should the STP UplinkFast feature be enabled?

Back 331

An access layer switch

Front 332

If used, the STP BackboneFast feature should be enabled where?

Back 332

all switches in the network

Front 333

What command is used to enable STP?

Back 333

spanning-tree [vlan-id]

Front 334

What command is used to set bridge priority for STP?

Back 334

spanning-tree vlan [vlan-id]priority [bridge-priority]

Front 335

What command is used to set port cost for STP?

Back 335

spanning-tree [vlan vlan-id] cost [cost]

Front 336

What commands are used to set the three STP timers?

Back 336

spanning-tree [vlan vlan-id] hello-time [seconds]
spanning-tree [vlan vlan-id] forward-time [seconds]
spanning-tree [vlan vlan-id] max-age [seconds]

Front 337

What command is used to set PortFast on an interface?

Back 337

spanning-tree portfast

Front 338

What command is used to set UplinkFast on a switch?

Back 338

spanning-tree uplinkfast

Front 339

What command is used to set BackboneFast on a switch?

Back 339

spanning-tree backbonefast

Front 340

What STP timer values can be automatically modified by setting the network diameter?

Back 340

Hello timer
Forward Delay timer
Max age timer

Front 341

Which STP timer determines how long a port stays in the Listening state? What is its default value?

Back 341

The Forward Delay timer; default 15 seconds

Front 342

What is the purpose of the Max Age timer?

Back 342

It sets the length of time received BPDUs are held if a neighboring switch is not heard from on a nondesignated port. After the Max Age timer expires, the BPDU for the neighbor is flushed
and that port enters the Listening state, eventually becoming the new Designated Port on the segment.

Front 343

What command can enable the STP PortFast feature on a switch? What configuration mode
must you enter first?

Back 343

spanning-tree portfast, in the interface configuration mode

Front 344

To prevent STP surprises you should always do what two things?

Back 344

(1) Configure one switch as a Root Bridge in a determined fashion and (2) Configure another switch as a secondary Root Bridge in case of primary Root Bridge failure.

Front 345

What command is used to change the STP bridge priority for an switch?

Back 345

Switch (config)# spanning-tree vlan [vlan-id] priority [bridge-priority]

Front 346

What command is used to let a switch become an STP Root by automatically choosing a Bridge Priority value?

Back 346

Switch(config)# spanning-tree vlan [vlan-id] root {primary | secondary}

Front 347

Which STP feature enables fast connectivity to be established on access layer switch ports to workstations that are booting up?

Back 347

PortFast

Front 348

Which STP feature enables fast uplink failover on an access layer switch when dual uplinks are connected into the distribution layer?

Back 348

UplinkFast

Front 349

Which STP feature enables fast convergence in the network backbone (core) after a Spanning Tree topology change occurs?

Back 349

BackboneFast

Front 350

PortFast shortens what two STP states?

Back 350

15 seconds Listening to Learning and 15 seconds Learning to Fowarding

Front 351

What command is used to view all possible STP parameters for all VLANs and ports?

Back 351

show spanning-tree

Front 352

Why is it important to protect the placement of the Root Bridge?

Back 352

To keep the STP topology stable

Front 353

Which feature protects a switch port from accepting superior BPDUs?

Back 353

STP root guard

Front 354

Which command can you use to enable STP root guard on a switch port?

Back 354

spanning-tree guard root

Front 355

Where should the STP root guard feature be enabled on a switch?

Back 355

Only ports where the Root Bridge should never appear

Front 356

Whiich feature protects a switch port from accepting BPDUs when PortFast is
enabled?

Back 356

STP BPDU guard

Front 357

Which feature can you use to identify when BPDUs are delayed as they pass through the topology?

Back 357

BPDU skew detection

Front 358

To maintain a loop-free STP topology, what should a switch uplink be protected against?

Back 358

A sudden loss of BPDUs

Front 359

What command can enable STP loop guard on a switch port?

Back 359

spanning-tree guard loop

Front 360

STP loop guard detects which condition?

Back 360

The sudden lack of BPDUs

Front 361

Which STP feature can actively test for the loss of the receive side of a link
between switches?

Back 361

UDLD

Front 362

UDLD must detect a unidirectional link before what can happen?

Back 362

STP moves the link to the forwarding state

Front 363

What must a switch do when it receives a UDLD message on a link?

Back 363

Echo the message back across the link.

Front 364

What command is used to enable root guard on an interface?

Back 364

spanning-tree guard root

Front 365

What command is used to enable BPDU guard on an interface?

Back 365

spanning-tree bpduguard enable

Front 366

What command is used to enable loop guard on an interface?

Back 366

spanning-tree guard loop

Front 367

What command is used to globally enable UDLD?

Back 367

udld [aggressive | enable | message time]

Front 368

What command is used to look for ports that have been put in an inconsistent STP state?

Back 368

show spanning-tree inconsistentports

Front 369

What command is used to show UDLD status?

Back 369

show udld [type mod/num]

Front 370

What command is used to re-enable all ports that UDLD has
errdisabled?

Back 370

udld reset

Front 371

Where should you apply root guard?

Back 371

Apply to ports where root is never expected.

Front 372

What condition must be met to keep a switch port in the blocking state?

Back 372

A constant flow of BPDUs. Without them, the switch thinks there is no need to block the port any longer.

Front 373

If a switch port is shown to be in the root-inconsistent state, what has happened on it?

Back 373

Root guard has detected someone advertising a BPDU that is superior to the current Root Bridge.

Front 374

When root guard has been triggered on a switch port, what must be done to enable the port for use again?

Back 374

Root guard will automatically allow the port to be moved through the STP states as soon as the superior BPDUs are no longer received.

Front 375

When BPDU guard is enabled on a switch port, what state will the port be put in if a BPDU is received on it?

Back 375

errdisable

Front 376

When BPDU guard has been triggered on a switch port, what must be done to enable the port for use again?

Back 376

If the errdisable timeout feature has been enabled, the switch will automatically put the switch port back into service after a set amount of time. Otherwise, the port will remain disabled until
you manually enable it again.

Front 377

What can happen if BPDUs are delayed or “skewed” as they pass along from switch to switch?

Back 377

A blocking link can be moved to forwarding, creating a bridging loop, if BPDUs are delayed or dropped.

Front 378

What action does BPDU skew detection take when late BPDUs are detected?

Back 378

None, other than generating a syslog message to alert someone of the skewed condition.

Front 379

When loop guard is enabled on a switch port, what state will the port be put in if BPDUs are noted to be missing?

Back 379

loop-inconsistent

Front 380

Can STP loop guard be enabled on all switch ports?

Back 380

Yes; only the non-designated ports will be affected by loop guard.

Front 381

When UDLD is enabled on a switch port, what else must be done to detect a unidirectional link on the port?

Back 381

Enable UDLD on the far-end switch on the same link.

Front 382

What is the difference between the UDLD normal and aggressive modes?

Back 382

Normal mode detects a unidirectional link condition and reports it. Aggressive mode detects the
condition, reports it, and moves the port to the errdisable state so that it can’t be used.

Front 383

What command enables UDLD aggressive mode on a switch interface?

Back 383

udld aggressive

Front 384

If two switches enable UDLD on the ports that have a common link, do their UDLD message times have to agree?

Back 384

No. The UDLD messages are just echoed back, so the message times are only locally
significant.

Front 385

UDLD should be used on switch ports with what type of media?

Back 385

Fiber-optic media

Front 386

Can UDLD be used on all switch ports without causing problems?

Back 386

Yes, although it is needed only on all fiber-based ports. The device on the far end of the port
connection must also support UDLD so that UDLD messages can be echoed back to the switch.

Front 387

What command would be used to display all ports that are disabled due to STP protection
features?

Back 387

show spanning-tree inconsistentports

Front 388

In STP, which switch port is the one port on a switch that is closest (lowest Root Path Cost) to the Root Bridge?

Back 388

root port

Front 389

In STP, which switch port is the port on a LAN segment that is closest to the Root; this port relays, or
transmits, BPDUs on down the tree?

Back 389

designated port

Front 390

In STP, which switch ports are ports that are neither Root nor Designated Ports?

Back 390

blocking ports

Front 391

In STP, which switch ports are candidate Root Ports (they are also close to the Root Bridge) but are in the blocking state; these ports are identified for quick use by the STP UplinkFast
feature?

Back 391

alternate ports

Front 392

In STP, which switch portds have no STP activity; these are ports with normal end user connections?

Back 392

forwarding ports

Front 393

The one central source of BPDUs in an STP domain is what?

Back 393

The root bridge

Front 394

BPDUs are regularly sent out when?

Back 394

Every two seconds

Front 395

Upon which standard is RSTP based?

Back 395

802.1w

Front 396

When a switch running RSTP receives an 802.1D BPDU, what happens?

Back 396

The switch begins to use 802.1D rules on that port.

Front 397

When does an RSTP switch consider a neighbor to be down?

Back 397

After three BPDUs are missed

Front 398

Which process is used during RSTP convergence?

Back 398

Synchronization

Front 399

What causes RSTP to view a port as a point-to-point port?

Back 399

Port duplex

Front 400

What event triggers a topology change with RSTP on a nonedge port?

Back 400

A port moves to the forwarding state.

Front 401

What standard defines the MST protocol?

Back 401

802.1s

Front 402

How many instances of STP are supported in the Cisco implementation of MST?

Back 402

16

Front 403

What switch command can be used to change from PVST+ to MST?

Back 403

spanning-tree mode mst

Front 404

What are the four RSTP port roles?

Back 404

 Root Port
 Designated Port
 Alternate Port
 Backup Port

Front 405

What are the three RSTP port states?

Back 405

 Discarding
 Learning
 Forwarding

Front 406

Which STP instance involved with MST is used to maintain a single loop-free topology for the entire network?

Back 406

CST (common spanning tree)

Front 407

Which STP instance involved with MST is used like CST to maintain a single, loop-free topology inside an MST region?

Back 407

Internal Spanning Tree (IST)

Front 408

Which STP instance involved with MST is used inside an MST region to maintain loop-free topologies for sets of mapped VLANs?

Back 408

MST Instances (MSTIs)

Front 409

What command is used to enable MST on a switch?

Back 409

spanning-tree mode mst

Front 410

What command is used to enter MST configuration mode?

Back 410

spanning-tree mst configuration

Front 411

What command is used to name the MST region?

Back 411

name [name]

Front 412

What command is used to map VLANs to an MST instance?

Back 412

instance [instance-id] vlan [vlan-list]

Front 413

What command is used to confirm new MST configuration changes?

Back 413

show pending

Front 414

In RSTP, can a switch port be a Designated Port and be in the Discarding state?

Back 414

Yes; RSTP removes the linkage between a port’s role and its state. In 802.1D, a Designated Port must be forwarding, but RSTP doesn’t make the same requirement.

Front 415

What two messages must be exchanged during RSTP synchronization?

Back 415

Proposal and Agreement

Front 416

In RSTP, after an agreement message is received from a neighboring switch, how much time elapses
before the port can begin forwarding? (Consider any timers that must expire or other conditions
that must be met.)

Back 416

The port will be moved to the Forwarding state immediately after the agreement message is
received. With RSTP, no other conditions are necessary because two switches have completed a quick handshake by exchanging proposal and agreement messages.

Front 417

In RSTP, after a switch receives news of a topology change, how long does it wait to flush entries out of
its CAM table?

Back 417

The switch flushes entries immediately, rather than employing the timer reduction that 802.1D uses.

Front 418

What command configures a port as an RSTP edge port?

Back 418

spanning-tree portfast

Front 419

Suppose interface FastEthernet 0/1 is in half-duplex mode, but you want it to be considered a
point-to-point link for RSTP. What command will accomplish this?

Back 419

spanning-tree link-type point-to-point

Front 420

What three parameters must be configured to uniquely define an MST region?

Back 420

The region name, configuration revision number, and the instance-to-VLAN mappings

Front 421

What parameter does a switch examine to see if its neighbors have the same VLAN to MST instance mappings? How is that information passed among switches?

Back 421

The VLAN-to-instance mapping is kept in a table of 4096 entries. This information is passed along in the MST BPDUs. Rather than passing the entire table, switches include only a digest
of their current table contents

Front 422

Which MST instance in a region corresponds to the CST of 802.1Q?

Back 422

The Internal Spanning Tree (IST) instance

Front 423

Which MST instance is the IST?

Back 423

IST is Instance 0. Instances 1 through 15 are available for other use.

Front 424

When an MST region meets a PVST+ domain, how is each MST instance propagated into
PVST+?

Back 424

The BPDUs from each instance are replicated and sent into all the appropriate VLANs in the PVST+ switch.

Front 425

Is it wise to assign VLANs to MST Instance 0? Why or why not?

Back 425

No. By default, all VLANs are mapped to Instance 0, the IST. You should select the number of instances needed and map all active VLANs to them. Otherwise, you can’t have full control over the topologies independent of IST and CST.

Front 426

A switch can interact with both 802.1D and RSTP. Can it run both PVST+ and MST
simultaneously?

Back 426

No. A switch can run either PVST+ or MST. If a switch is running MST, it can interact and interoperate with PVST+, 802.1D, and RSTP.

Front 427

In what RSTP port state are incoming frames simply dropped; no MAC addresses are learned?

Back 427

discarding

Front 428

In what RSTP port state are incoming frames dropped, but MAC addresses are learned?

Back 428

learning

Front 429

In what RSTP port state are incoming frames forwarded according to MAC addresses that have been (and are being) learned?

Back 429

forwarding

Front 430

What are the three RSTP port states?

Back 430

discarding
learning
forwarding

Front 431

In RSTP, how long does it take a switch can detect a neighbor failure?

Back 431

In three Hello intervals (default 6 seconds)

Front 432

What are the three RSTP port types?

Back 432

Edge, root and point to point

Front 433

MST is built on the concept of what?

Back 433

MST is built on the concept of mapping one or more VLANs to a single STP instance. Multiple instances of STP can be used (hence the name MST), with each instance supporting a different group of VLANs.

Front 434

How many interfaces are needed in a “router on a stick” implementation for InterVLAN routing among four VLANs?

Back 434

1

Front 435

Which command configures a switch port for Layer 2 operation?

Back 435

switchport

Front 436

Which command configures a switch port for Layer 3 operation?

Back 436

no switchport

Front 437

What information must be learned before CEF can forward packets?

Back 437

The contents of the routing table

Front 438

Assume CEF is active on a switch. What happens to a packet that arrives needing
fragmentation?

Back 438

The packet is sent to the Layer 3 engine.

Front 439

Suppose a host sends a packet to a destination IP address, and the CEF-based switch does not yet have a valid MAC address for the destination. How is the ARP entry (MAC address) of the next-hop destination in the FIB obtained?

Back 439

CEF must wait until the Layer 3 engine sends an ARP request for it.

Front 440

During a packet rewrite, what happens to the source MAC address?

Back 440

It is changed to the MAC address of the outbound Layer 3 switch interface.

Front 441

What Spanning Tree Protocol is used for fallback bridging?

Back 441

VLAN-bridge

Front 442

What command can you use to view the CEF FIB table contents?

Back 442

show ip cef

Front 443

What command is used to define an SVI?

Back 443

interface vlan [vlan-id]

Front 444

What command puts a port into Layer 2 mode?

Back 444

switchport

Front 445

What command puts a port into Layer 3 mode?

Back 445

no switchport

Front 446

What component of CEF contains routing and next-hop information; lookups
are performed according to longest match IP prefix?

Back 446

Forwarding Information Base (FIB)

Front 447

What component of CEF contains Layer 2 address information for next-hop FIB entries that are one
hop away?

Back 447

Adjacency table

Front 448

What command is used to show a Layer 2 port status?

Back 448

show interface [type mod/num] switchport

Front 449

What command is used to show a Layer 3 port status?

Back 449

show interface [type mod/num]

Front 450

What command is used to show an SVI status?

Back 450

show interface vlan [vlan-id]

Front 451

What command is used to view the FIB contents?

Back 451

show ip cef [type mod/num]

Front 452

What command is used to show fallback bridge group status?

Back 452

show bridge group

Front 453

To configure an SVI, what commands are needed?

Back 453

(First, make sure the VLAN is defined on the switch.)
interface vlan [vlan-id]
ip address [ip-address mask]
no shutdown

Front 454

What is the source of FIB information?

Back 454

The routing table, as computed by the Layer 3 engine portion of a swi

Front 455

How often is the FIB updated?

Back 455

As needed; it is downloaded or updated dynamically by the Layer 3 engine whenever the
routing topology changes or an ARP entry changes.

Front 456

What is meant by the term “CEF punt?”

Back 456

A packet can’t be forwarded or switched by CEF directly because it needs further processing.
The packet is “punted” to the Layer 3 engine, effectively bypassing CEF for a more involved resolution.

Front 457

What happens to the FIB when distributed CEF (dCEF) is used?

Back 457

It is simply replicated to each of the independent CEF engines. The FIB itself remains intact, so that each engine receives a duplicate copy.

Front 458

What happens during a “CEF glean” process?

Back 458

The MAC address (ARP reply) for a next-hop FIB entry is not yet known. The Layer 3 engine must generate an ARP request and wait for a reply before CEF forwarding can continue to that destination.

Front 459

What does a multilayer switch do to the IP TTL value just before a packet is forwarded?

Back 459

The TTL is decremented by one, as if a router had forwarded the packet.

Front 460

What is fallback bridging?

Back 460

On switch platforms that cannot multilayer switch (route) all routable protocols, those protocols
can be transparently bridged between VLANs instead.
13.

Front 461

What does SVI stand for?

Back 461

Switched Virtual Interface.

Front 462

What do multilayer switches share when running HSRP?

Back 462

an IP address

Front 463

What HSRP group uses the MAC address 0000.0c07.ac11?

Back 463

Group 17 (hex)

Front 464

How many routers are in the Standby state in an HSRP group?

Back 464

1

Front 465

What VRRP group uses the virtual MAC address 0000.5e00.01ff?

Back 465

group 255

Front 466

What is the best protocol for load balancing redundant gateways?

Back 466

GLBP

Front 467

What GLBP function answers ARP requests?

Back 467

AVG

Front 468

By default, which virtual MAC address will be sent to the next client that looks
for the virtual gateway?

Back 468

The next virtual MAC address in the sequence

Front 469

In SLB, with what must a virtual server be linked?

Back 469

A server farm

Front 470

In SLB, what command specifies the IP address of a server in a server farm?

Back 470

real [ip address]

Front 471

What are the two router roles in HSRP?

Back 471

Active router, standby
router

Front 472

What are the two router roles in VRRP?

Back 472

Master router, backup
router

Front 473

What are the two router roles in GLBP?

Back 473

AVG, AVF

Front 474

What is the Virtual router MAC
address for VRRP?

Back 474

0000.5e00.01xx

Front 475

What is the Virtual router MAC
address for HSRP?

Back 475

0000.0c07.acxx

Front 476

What HSRP command is used to set the HSRP priority?

Back 476

standby [group] priority [priority]

Front 477

What HSRP command is used to
allow router preemption?

Back 477

standby [group] preempt [delay seconds]

Front 478

What HSRP command is used to
adjust priority by tracking an interface?

Back 478

standby [group] track [type mod/num decrementvalue]

Front 479

What HSRP command is used to
assign the virtual router address?

Back 479

standby group ip [ip-address] [secondary]

Front 480

What VRRP command is used to
assign a VRRP router priority (default 100)?

Back 480

vrrp [group] priority [level]

Front 481

What VRRP command is used to
learn the advertisement interval from the master router?

Back 481

vrrp [group] timers learn

Front 482

What VRRP command is used to
disable preempting (default is to preempt)?

Back 482

no vrrp group preempt

Front 483

What VRRP command is used to
assign a virtual IP address?

Back 483

vrrp [group] ip [ip-address] [secondary]

Front 484

What GLBP command is used to assign a GLBP priority?

Back 484

glbp group priority level

Front 485

What GLBP command is used to choose the load-balancing
method?

Back 485

glbp [group] load-balancing [round-robin | weighted | host-dependent]

Front 486

What SLB command is used to name a server farm?

Back 486

ip slb serverfarm [serverfarm-name]

Front 487

What SLB command is used to choose a load-balancing method?

Back 487

predictor {roundrobin | leastconns}

Front 488

What SLB command is used to identify a real server?

Back 488

real [ip-address]

Front 489

What SLB command is used to
name the virtual server?

Back 489

ip slb vserver [virtual-server-name]

Front 490

What SLB command is used to link the virtual server to a server farm?

Back 490

serverfarm [serverfarm-name]

Front 491

What SLB command is used to enable the virtual server for use?

Back 491

inservice

Front 492

A multilayer switch has been configured with the command standby 5 priority 120. What
router redundancy protocol is being used?

Back 492

HSRP

Front 493

What feature can you use to prevent other routers from accidentally participating in an HSRP group?

Back 493

HSRP authentication

Front 494

What command can configure an HSRP group to use a virtual router address of
192.168.222.100?

Back 494

standby 1 ip 192.168.222.100

Front 495

How many HSRP groups are needed to load balance traffic over two routers?

Back 495

2

Front 496

What load-balancing methods can GLBP use?

Back 496

Round robin, weighted, host dependent

Front 497

What command can you use to see the status of the active and standby routers on the VLAN 171 interface?

Back 497

show standby vlan 171

Front 498

How many GLBP groups are needed to load balance traffic over four routers?

Back 498

1

Front 499

When should you use SLB?

Back 499

When load balancing is needed for clients to access a server farm.

Front 500

What does GLBP stand for?

Back 500

Gateway Load Balancing Protocol (GLBP)

Front 501

What does VRRP stand for?

Back 501

Virtual Router Redundancy Protocol (VRRP)

Front 502

To what multicast address does HSRP send its hello messages?

Back 502

HSRP sends its hello messages to the multicast destination 224.0.0.2

Front 503

Which router becomes the active router for an HSRP group?

Back 503

The router with the highest priority value (255 is highest) becomes the active router for the group.

Front 504

If all HSRP router priorities are equal or set to the default value, which router on the becomes the active router?

Back 504

the router with the highest IP address on the HSRP interface becomes the active router.

Front 505

What is the HSRP state sequence?

Back 505

Disabled, Init, Listen, Speak, Standby, and, finally,
Active.

Front 506

By default, how often are HSRP hellos sent?

Back 506

By default, hellos are sent every 3 seconds.

Front 507

Was is the default holdtime for HSRP before the standby router goes active?

Back 507

10 seconds

Front 508

How often are VRRP advertisements sent?

Back 508

VRRP advertisements are sent at 1-second intervals.

Front 509

In GLBP, what is an AVG?

Back 509

The active virtual
gateway (AVG). This router has the highest priority value, or the highest IP address in the group, if
there is no highest priority. The AVG answers all ARP requests for the virtual router address. Which
MAC address it returns depends upon which load-balancing algorithm it is configured to use. In any
event, the virtual MAC address supported by one of the routers in the group is returned.

Front 510

In GLBP, what is an AVF?

Back 510

The active virtual forwarder (AVF), forwarding traffic received on its virtual MAC
address. Other routers in the group serve as backup or secondary virtual forwarders, in case the AVF fails. The AVG also assigns secondary roles.

Front 511

How does GLBP do Load Balancing?

Back 511

By handing out virtual router MAC addresses to clients in a
deterministic fashion.

Front 512

What are the three load-balancing methods that can be used in a GLBP group?

Back 512

Round robin
Weighted
Host-dependent

Front 513

SLB load balancing can be
configured as what two methods?

Back 513

Weighted round-robin
Weighted least connections

Front 514

How many sources are typically present in a multicast group?

Back 514

1

Front 515

How many unique multicast IP addresses can correspond to one multicast MAC address?

Back 515

32

Front 516

What test is performed before a multicast packet can be forwarded?

Back 516

Reverse Path Forwarding

Front 517

Which protocol registers hosts for multicast group membership?

Back 517

IGMP

Front 518

A host sends Internet Group Management Protocol (IGMP) packets to what device?

Back 518

a router

Front 519

If a multicast group has recipients on every subnet, which of the PIM modes should be used?

Back 519

dense mode

Front 520

Which type of tree structure is built for sparse mode multicast routing?

Back 520

a shared tree

Front 521

What router maintains the RP-to-group correlation for Auto-RP in PIMv1?

Back 521

Mapping agent

Front 522

What router advertises candidate RP routers in PIMv2?

Back 522

Bootstrap router

Front 523

In what kind of "cast" are packets sent from one source host address to a single destination host address?

Back 523

unicast

Front 524

In what kind of "cast" are packets sent from one source host address to a special group-based destination address?

Back 524

multicast

Front 525

In what kind of "cast" are packets sent from one source host address to a broadcast destination address?

Back 525

broadcast

Front 526

What command is used to enable multicast routing?

Back 526

ip multicast-routing

Front 527

What command is used to use PIM Dense Mode on an
interface?

Back 527

ip pim dense-mode

Front 528

What command is used to use PIM Sparse Mode on an
interface?

Back 528

ip pim sparse-mode

Front 529

What command is used to use PIM Sparse-Dense Mode on an
interface?

Back 529

ip pim sparse-dense-mode

Front 530

What command is used to define a PIMv1 RP?

Back 530

ip pim rp-address [ip-address]

Front 531

What technology allows a switch to intercept IGMP messages to learn of group members and their port locations?

Back 531

IGMP snooping

Front 532

What technology allows a router to relay IGMP join and leave requests to Layer 2 switches. The switches
then learn of group members and their port locations?

Back 532

CGMP

Front 533

What command defines a PIMv2 border router?

Back 533

ip pim border

Front 534

By default, what does a router or Layer 3 switch do with multicast packets?

Back 534

It drops them because multicast routing is not enabled by default.

Front 535

By default, what does a Layer 2 switch do with a multicast packet?

Back 535

It floods the packet out all ports on the source VLAN, as if it were a broadcast packet.

Front 536

What high-order bit combination signals that an IP address is used for multicast?

Back 536

1110

Front 537

What IP multicast address range is set aside for use only on the local network segment?

Back 537

224.0.0.0 – 224.0.0.255

Front 538

For the RPF check, the source IP address is looked up in the unicast routing table. To forward the packet, what should the result of the test be?

Back 538

The unicast route to the source must be out the interface where the packet arrived.

Front 539

What important difference exists between IGMPv1 and IGMPv2?

Back 539

Hosts can request to leave a multicast group immediately with IGMPv2. IGMPv1 doesn’t have any mechanism for leaving a group, other than an aging-out process.

Front 540

To join a multicast group, what type of message is sent? Where is this message sent?

Back 540

An IGMP Membership Report is sent. The IGMP message is with a destination address of the multicast group itself so that the nearest multicast router will receive it.

Front 541

What is the purpose of the IGMP Querier?

Back 541

It is a router that periodically asks all hosts if any of them want to join the multicast group.
Interested hosts must respond with a Membership Report.

Front 542

For PIM Dense Mode, how is the multicast tree built?

Back 542

The source is the root of the tree, and all Dense Mode routers are included by default. After all of these have joined the group, a pruning phase occurs so that routers with no member hosts are pruned off the tree.

Front 543

Where is the root of the PIM Sparse Mode tree located?

Back 543

At a Rendezvous Point (RP) router

Front 544

With PIM Sparse-Dense Mode, is the PIM mode determined per interface or per group?

Back 544

Per group. If the group has an RP, Sparse Mode is used; otherwise, Dense Mode is used.

Front 545

What routing table is used for PIM?

Back 545

The unicast routing table is used. PIM does not build or maintain its own multicast routing table.

Front 546

What command is used to configure an interface for the hybrid PIM mode?

Back 546

ip pim sparse-dense-mode

Front 547

When a switch performs IGMP snooping, what is it snooping for?

Back 547

It listens to all IGMP membership reports so that it can learn the location of hosts joining and
leaving multicast groups.

Front 548

What else does a Layer 2 switch need when it is configured for CGMP?

Back 548

A multicast router. The router relays group join and leave requests as CGMP packets that the switch can use.

Front 549

When should IGMP snooping and CGMP be used together on a switch?

Back 549

Never; they are mutually exclusive features.

Front 550

Multicast MAC addresses always begin with what?

Back 550

0100.5e

Front 551

What is the complete multicast IP space?

Back 551

224.0.0.0 through 239.255.255.255

Front 552

What is the multicast link-local IP space address?

Back 552

Link-local addresses (224.0.0.0 through 224.0.0.255)—Used by network protocols only on the local network segment. Routers do not forward these packets.
This space includes the all-hosts address 224.0.0.1, all-routers 224.0.0.2, OSPF-routers 224.0.0.5, and so on. These are also known as fixed-group addresses because they are wellknown and predefined.

Front 553

What command enables multicast routing?

Back 553

Switch(config)# ip multicast-routing

Front 554

What does IGMP stand for?

Back 554

Internet Group Management Protocol (IGMP)

Front 555

How does a host join a multicast group?

Back 555

A host can join a multicast group by sending a request to its local router.

Front 556

What is a routing protocol that can be used for forwarding multicast traffic?

Back 556

Protocol Independent Multicast (PIM)

Front 557

What are the three modes of PIM?

Back 557

PIM Dense Mode
PIM Sparse Mode
PIM Sparse-Dense Mode

Front 558

What does PIM stand for?

Back 558

Protocol Independent Multicast (PIM)

Front 559

Which PIM version uses BSRs (bootstrap routers)?

Back 559

PIM Version 2

Front 560

What technology allows a router to become a multicast “hearing aid” for a switch that is IGMP snooping “hearing impaired"?

Back 560

CGMP - Cisco Group Management Protocol

Front 561

What QoS model reserves bandwidth end-to-end?

Back 561

IntServ

Front 562

Where is QoS implemented in the DiffServ model?

Back 562

On each network device (per-hop)

Front 563

At what layer of the OSI model is class of service (CoS) used to pass QoS information?

Back 563

Layer 2

Front 564

What does the DSCP name “EF” mean?

Back 564

Expedited Forwarding

Front 565

In the DSCP codepoint name “AF31,” what does the “3” digit represent?

Back 565

Class Selector

Front 566

What element of DiffServ QoS identifies traffic?

Back 566

Classification

Front 567

When a switch is configured at a trust boundary, what can be trusted?

Back 567

CoS values

Front 568

When would you use the QoS scheduling process in a switch?

Back 568

To determine the order that packets are forwarded

Front 569

What methods unconditionally drops packets when a queue is full?

Back 569

tail drop

Front 570

How does WRED detect and avoid congestion?

Back 570

It randomly drops packets.

Front 571

A switch port has two standard queues, two WRED thresholds, and one strict priority queue. How can its queue type be written?

Back 571

1p2q2t (remember pqt)

Front 572

What are some of the problems that QoS can help relieve?

Back 572

Packet delay, packet loss, jitter

Front 573

Which protocol is used to reserve network resources in the IntServ QoS model?

Back 573

RSVP

Front 574

What protocol is used to maintain the DiffServ QoS model?

Back 574

None; DiffServ is defined as a per-hop behavior, so no communication is needed between networking devices.

Front 575

What range of values can the CoS field contain?

Back 575

0 through 7 because CoS is three bits in length.

Front 576

How is the CoS information passed from LAN switch to LAN switch?

Back 576

Only across trunking links, where the CoS is contained in the trunk encapsulation.

Front 577

How is the IP Precedence field related to the DSCP field?

Back 577

They are both located in the same byte of the IP header. The three IP Precedence bits are actually the same as the first 3 bits of the DSCP (the Class Selector). However, the DSCP contains three additional bits for greater flexibility.

Front 578

If a packet contains the DSCP codepoint name “AF31,” what would the IP Precedence value be?

Back 578

3; the Class Selector bits (“3” in the codepoint name) are the same as the IP Precedence bits.

Front 579

If a switch port is configured as “untrusted,” what is the resulting CoS value of incoming packets?

Back 579

Each packet’s CoS is overwritten with the default CoS value of the switch port itself. In the default case, the port’s CoS is zero.

Front 580

What method is used for scheduling in Catalyst switches?

Back 580

Weighted Round Robin (WRR)

Front 581

Name two methods that are used for congestion avoidance.

Back 581

Tail drop or Weighted Random Early Detection (WRED)

Front 582

When are packets dropped from the strict priority queue on an interface?

Back 582

Packets are never dropped from the priority queue by WRED. The only condition that causes packets to be dropped is when the priority queue is full. In that case, packets are dropped by the tail drop method.

Front 583

What is the disadvantage of using the tail drop method to avoid congestion?

Back 583

Tail drop waits until the queue is full before dropping the latest arriving packets. This tends to avoid congestion after congestion occurs. The main disadvantage is with TCP connections,
which begin to back off and enter the slow-start state once tail drop begins. All active TCP connections
will do this simultaneously, synchronized with each other. This causes a widespread
throughput issue and makes the overall network utilization oscillate

Front 584

A switch port has a queue type 1p1q4t. What does this mean?

Back 584

The port has one strict-priority queue (1p), one standard queue (1q), and four WRED thresholds
per standard queue (4t).

Front 585

If a switch port has a queue type 1p2q2t, what is the strict priority queue’s queue number?

Back 585

The strict-priority queue is queue 3. (The low-priority standard queue is 1, the high-priority standard queue is 2.)

Front 586

Variation in delay is called what?

Back 586

jitter

Front 587

The total delay from start to finish is called what?

Back 587

latency

Front 588

What are the three basic types of QoS that can be used in a network?

Back 588

Best-effort delivery
Integrated Services model
Differentiated Services model

Front 589

How is CoS marked in a IEEE 802.1Q trunk?

Back 589

Each frame is tagged with a 12-bit VLAN ID and a User field. The User field
contains three 802.1p priority bits that indicate the frame CoS, a unitless value ranging from 0
(lowest-priority delivery) to 7 (highest-priority delivery). Frames from the native VLAN are not tagged at all (no VLAN ID or User field), so they receive a default CoS that is configured on the receiving switch.

Front 590

How is CoS marked in an ISL trunk?

Back 590

Each frame is tagged with a 15-bit VLAN ID. In addition, next to the frame Type field is a 4-bit User field. The lower three bits of the User field are used as a CoS
value. Although ISL is not standards-based, Catalyst switches make CoS seamless by copying the 802.1p CoS bits from an 802.1Q trunk into the User CoS bits of an ISL trunk. This allows CoS information to propagate along trunks of differing encapsulations.

Front 591

The Differentiated Service Code Point (DSCP)has how many bits?

Back 591

6 bits

Front 592

DiffServ QoS examines what to make decisions?

Back 592

The Differentiated Service Code Point (DSCP), which has 6 bits

Front 593

Are the ToS and DS bytes the same?

Back 593

Yes

Front 594

The DSCP value is broken up into what?

Back 594

A 3-bit Class Selector and a 3-bit Drop Precendence value.

Front 595

What is the decimal equivalent of codepoint EF?

Back 595

46

Front 596

What is the decimal equivalent of codepoint AF41?

Back 596

34

Front 597

What is the decimal equivalent of codepoint AF31?

Back 597

26

Front 598

What is the decimal equivalent of codepoint AF21?

Back 598

18

Front 599

What is the decimal equivalent of codepoint AF11?

Back 599

10

Front 600

Most switches have what two types of ingress queues?

Back 600

a strict priority queue
and a standard queue

Front 601

What are the two types of QoS Policers?

Back 601

microflow and aggregate)

Front 602

By default, how are packets with CoS markings placed in the various queues.

Back 602

By default, packets with CoS 0 through 3 are assigned to the first standard queue, while CoS 4 through 7 go in the second standard queue.
CoS 5 goes to the strict priority queue

Front 603

The overall effect of tail dropping is that all active TCP connections go into congestion back-off and
then slow-start. What is this called?

Back 603

global synchronization.

Front 604

What does WRED attempt to do to alleviate congestion?

Back 604

WRED attempts to randomly drop packets that are already in the queue so that the queue cannot become full.

Front 605

The lowest-priority standard queue is what?

Back 605

The lowest-priority standard queue is always Queue 1

Front 606

The number of strict priority queues is notated how?

Back 606

p

Front 607

The number of configurable WRED thresholds per standard queue is notated how?

Back 607

t

Front 608

The number of standard queues is notated how?

Back 608

q

Front 609

Does the priority queue ever have threshold?

Back 609

The priority queue never has a threshold because no packets are ever proactively dropped

Front 610

By default, how does a switch port treat incoming QoS information?

Back 610

It is not trusted.

Front 611

What command can configure an interface to trust only the inbound DSCP information?

Back 611

mls qos trust dscp

Front 612

Which command defines what traffic will be identified for a QoS policy?

Back 612

class-map

Front 613

What QoS classification method can match traffic flows that use dynamic UDP or TCP port
numbers?

Back 613

NBAR

Front 614

Which QoS configuration command can contain actions to take on classified traffic?

Back 614

policy-map

Front 615

What command can apply a QoS policy to an interface?

Back 615

service-policy [policy-name]

Front 616

How many QoS policy maps can be applied to an interface?

Back 616

Two; one in each inbound or outbound direction.

Front 617

What command would enable WRED on interface queue 2?

Back 617

wrr-queue random-detect 2

Front 618

A switch port has a minimum WRED threshold configured at 25 percent. If the queue stays
below 25 percent, what can happen to the queued packets?

Back 618

They can never be dropped.

Front 619

What two ways can QoS trust be configured on a switch?

Back 619

Per-interface and per-policy

Front 620

If all QoS trust decisions will be applied as part of a QoS policy, what command should you use on an interface?

Back 620

no mls qos trust; All trust must be disabled on the interface because the policy will enable any specific trust conditions that are configured.

Front 621

When a QoS class map is configured, what types of commands must also be used?

Back 621

match commands, to match specific types of traffic

Front 622

Name two methods that you can use to identify or classify traffic.

Back 622

Matching can be based on traffic that is permitted by an access list and on protocols identified by NBAR.

Front 623

What command can classify traffic with an extended IP access list?

Back 623

match access-group name [access-list]

Front 624

What command can classify traffic with NBAR?

Back 624

match protocol [protocol-name]

Front 625

What does a QoS policy map contain?

Back 625

It contains references to class maps that identify types of traffic and actions to take as a result of each class map.

Front 626

When a policy map is applied to an interface, does it control both inbound and outbound traffic?

Back 626

The policy map must be applied in one direction only, each time it is configured on the interface.
It can control only inbound or outbound traffic, unless it is applied twice to the interface—once in each direction.

Front 627

What is the first command keyword used to configure WRED congestion avoidance?

Back 627

wrr-queue; This seems surprising because wrr-queue is also used to configure scheduling. However, Catalyst switches use the same components to schedule and perform WRED because both involve egress queue operations.

Front 628

What QoS information is used to map packets into the egress queues of a switch port?

Back 628

CoS, through the use of a CoS-to-queue mapping function

Front 629

What command can display the QoS and queue information about a switch port?

Back 629

show queueing interface

Front 630

To enable QoS on a switch, use what global configuration command?

Back 630

mls qos

Front 631

On each interface where consistent QoS trust is to be defined, what is the interface
configuration command?

Back 631

Switch(config-if)# mls qos trust {cos | dscp | ip-precedence}

Front 632

If you choose to not trust any QoS information (the default condition), you use what interface
configuration command?

Back 632

Switch(config-if)# no mls qos trust

Front 633

CoS 5 maps to what DSCP value?

Back 633

EF

Front 634

What 3 steps define QoS policy?

Back 634

1. QoS classes are defined to classify (identify) specific traffic.
2.One or more QoS policies are defined to reference or group multiple QoS classes as a single entity.
3.Each egress interface can be assigned one QoS policy in each direction.

Front 635

What 3 steps define QoS policy?

Back 635

1. QoS classes are defined to classify (identify) specific traffic.
2.One or more QoS policies are defined to reference or group multiple QoS classes as a single entity.
3.Each egress interface can be assigned one QoS policy in each direction.

Front 636

What 3 steps define QoS policy?

Back 636

1. QoS classes are defined to classify (identify) specific traffic.
2.One or more QoS policies are defined to reference or group multiple QoS classes as a single entity.
3.Each egress interface can be assigned one QoS policy in each direction.

Front 637

What command defines a QoS class to classify Traffic?

Back 637

Switch(config)# class-map [class-name] [match-all | match-any]

Front 638

What command is used to classifying traffic with an Access List?

Back 638

Switch(config-cmap)# match access-group name [access-list]

Front 639

To match a traffic flow with NBAR, use what class map configuration command?

Back 639

Switch(config-cmap)# match protocol [protocol-name]

Front 640

What QoS feature can recognize traffic from several
applications, whether the UDP or TCP ports are statically or dynamically assigned?

Back 640

NBAR

Front 641

What does NBAR stand for?

Back 641

Network-Based Application
Recognition

Front 642

What command is used to define a QoS policy?

Back 642

Switch(config)# policy-map [policy-name]

Front 643

What interface configuration command is used to begin using a QoS policy?

Back 643

Switch(config-if)# service-policy [input | output] [policy-name]

Front 644

Catalyst switches support what scheduling algorithm?

Back 644

Weighted Round Robin (WRR)

Front 645

By default, interfaces with two standard queues are assigned what weights?

Back 645

4 and 255. The second queue receives about 64 times the amount of data transmitted on its turn for every one unit of data from the first queue.

Front 646

After the switch determines which egress port each packet will use when exiting, what values are mapped into CoS values?

Back 646

internal DSCP values

Front 647

What interface configuration command enables the strict-priority queue?

Back 647

priority-queue out

Front 648

If an interface is configured to consider all inbound QoS information as untrusted, what are the inbound CoS and DSCP values set to?

Back 648

both are set to 0

Front 649

What interface command would be used so that inbound DSCP information will be used as the trusted quantity?

Back 649

mls qos trust dscp

Front 650

In a switch, what always used to decide how packets are queued and scheduled for transmission in the egress queues?

Back 650

CoS values

Front 651

For a Catalyst switch to offer inline power to a device, what must occur?

Back 651

The switch must detect that the device needs inline power.

Front 652

What command can enable inline power to a switch interface?

Back 652

power inline auto

Front 653

What does a Cisco IP Phone contain to allow it to pass both voice and data packets?

Back 653

An internal three-port switch

Front 654

How can voice traffic be kept separate from any other data traffic through an IP Phone?

Back 654

A special-case 802.1Q trunk is used to the switch.

Front 655

What command configures an IP Phone to use VLAN 9 for voice traffic?

Back 655

switchport voice vlan 9

Front 656

What is the default voice VLAN condition for a switch port?

Back 656

switchport voice vlan none

Front 657

If the switchport voice vlan 50 command has been used, what VLAN numbers will the voice and PC data be carried over, respectively?

Back 657

VLAN 50, native VLAN

Front 658

When a PC is connected to the PC switch port on an IP Phone, how is QoS trust handled?

Back 658

The Catalyst switch instructs the IP Phone how to trust the PC QoS information.

Front 659

An IP Phone should mark all incoming traffic from an attached PC to have CoS 1. What command is used for this?

Back 659

switchport priority extend cos 1

Front 660

Which switch port queue should voice bearer packets be placed in?

Back 660

Strict-priority queue

Front 661

What command can verify the inline power status of each switch port?

Back 661

show power inline

Front 662

What command can verify the voice VLAN used by a Cisco IP Phone?

Back 662

show interface switchport

Front 663

How does a Catalyst switch detect that a connected device is capable of using inline power?

Back 663

The device must first loop the Ethernet connection’s transmit and receive pairs. The switch can then hear its own test tone, confirming that the device does indeed need inline power. After the
power is enabled on the port, the switch and the device can exchange CDP messages so that the amount of power can be adjusted.

Front 664

What type of trunk can be used between a Catalyst switch port and a Cisco IP Phone?

Back 664

A special-case 802.1Q trunk with only two VLANs

Front 665

When a trunk is used on an IP Phone, on which VLAN is the data from an attached PC carried?

Back 665

PC data is always carried over the native (untagged) VLAN in the trunk. Voice packets can be carried over the native VLAN, too, or over a unique voice VLAN.

Front 666

What is the difference between the VVID and the PVID?

Back 666

VVID refers to the Voice VLAN ID, whereas PVID refers to the Port VLAN ID.

Front 667

What is the advantage of using the switchport voice vlan dot1p command?

Back 667

Voice traffic is carried over VLAN 0 on the IP Phone trunk, so a unique voice VLAN is not
necessary. This can be an advantage when a new VLAN can’t be added to a network or switch. CoS information is still carried over the trunk in the 802.1p field.

Front 668

By default, does a Cisco IP Phone trust QoS information from an attached PC?

Back 668

No. The phone will overwrite all QoS information (both CoS and DSCP) to 0, considering the PC an untrusted source.

Front 669

The command switchport priority extend cos 5 is entered for a switch port. Is this a good decision? Why or why not?

Back 669

Probably not. After that is done, all packets from an attached PC will be marked with CoS 5— the same value the phone gives to its voice bearer packets. Any upstream switches will be unable to distinguish the two types of traffic just by examining the CoS value.

Front 670

How can a switch classify VoIP voice bearer packets that are carried by RTP?

Back 670

RTP uses negotiated UDP port numbers, so access lists can’t be used. Instead, NBAR is able to classify the traffic by a stateful inspection. The match protocol rtp command can be used for this

Front 671

What command can verify the QoS trust relationship between an IP Phone and its attached PC?

Back 671

show mls qos interface

Front 672

Inline power is provided over what pairs?

Back 672

pairs 2 and 3, RJ-45 pins 1,2 and 3,6

Front 673

If the username command is used in a switch configuration, what method of authentication is implied?

Back 673

local

Front 674

What command should be used to configure a vty line to use the “myservers” authentication method list?

Back 674

login authentication myservers

Front 675

If a user needs to be in the privileged EXEC or enable mode, which part of AAA must succeed?

Back 675

Authorization

Front 676

Which switch feature can grant access through a port only if the host with MAC address 0005.0004.0003 is connected?

Back 676

Port security

Front 677

Port security is being used to control access to a switch port. Which command will put the port into the errdisable state if an unauthorized station connects?

Back 677

switchport port-security violation shutdown

Front 678

If port security is left to its default configuration, how many different MAC addresses can be learned at one time on a switch port?

Back 678

1

Front 679

What protocol is used for port-based authentication?

Back 679

802.1x

Front 680

When 802.1x is used for a switch port, where must it be configured?

Back 680

Switch port and client PC

Front 681

When port-based authentication is globally enabled, what is the default behavior for all switch
ports?

Back 681

Allow all connections without authentication.

Front 682

After port-based authentication is enabled, what method is available for a user to authenticate?

Back 682

802.1x client

Front 683

What does the acronym “AAA” stand for?

Back 683

Authentication, authorization, and accounting

Front 684

What external methods of authentication does a Catalyst switch support?

Back 684

RADIUS and TACACS+

Front 685

A RADIUS server is located at IP address 192.168.199.10. What command can be used to
configure a Catalyst switch to find the server?

Back 685

radius-server host 192.168.199.10

Front 686

A Catalyst switch should be configured to authenticate users against RADIUS servers first, followed by TACACS+ servers. What command can define the authentication methods? Make sure users can still authenticate if none of the servers are available.

Back 686

aaa authentication login default radius tacacs+ local

Front 687

When the 802.1x force-authorized keyword is used, how does the switch react to users attempting to connect?

Back 687

The switch always authorizes any connecting user, without any authentication.

Front 688

Can more than one host be authenticated on a single switch port with port-based authentication?

Back 688

Yes, if the dot1x multi-hosts command is configured on the switch port interface.

Front 689

What command is used to enable AAA on the switch.

Back 689

Switch(config)# aaa new-model

Front 690

To configure port security on an access layer switch port, begin by enabling it with what
interface configuration command?

Back 690

Switch(config-if)# switchport port-security

Front 691

With port security, what command would statically define one or more MAC addresses on an interface?

Back 691

Switch(config-if)# switchport port-security mac-address [mac-addr]

Front 692

What three options do you have if a port security violation occurs?

Back 692

shutdown, restrict, protect

Front 693

You must configure each switch port that will use 802.1x. What interface configuration command is used to set the authentication state?

Back 693

Switch(config-if)# dot1x port-control {force-authorized | force-unauthorized | auto}

Front 694

What command enables port security on an interface?

Back 694

switchport port-security

Front 695

What command globally enables 802.1x?

Back 695

dot1x system-auth-control

Front 696

What can be used on a switch to filter packets even if they are not routed to another Layer 3
interface?

Back 696

VLAN access lists

Front 697

In what part of a Catalyst switch are VLAN ACLs implemented?

Back 697

TCAM

Front 698

What command can implement a VLAN ACL called “test?”

Back 698

vlan access-map test

Front 699

After a VACL is configured, where is it applied?

Back 699

Globally on a VLAN

Front 700

What type of private VLAN is the most restrictive?

Back 700

Isolated VLAN

Front 701

The vlan 100 command has just been entered. What is the next command needed to configure VLAN 100 as a secondary isolated VLAN?

Back 701

private-vlan isolated

Front 702

What type of port configuration should you use for private VLAN interfaces on a router?

Back 702

Promiscuous

Front 703

What technology allows a port to be mirrored to another port on the same switch?

Back 703

SPAN

Front 704

What must be used to connect switches used for RSPAN?

Back 704

An RSPAN VLAN over a trunk

Front 705

What is the most important difference between an RSPAN VLAN and a regular VLAN?

Back 705

The RSPAN VLAN disables MAC address learning

Front 706

To configure an RSPAN session’s source switch, what is used for the session destination?

Back 706

The RSPAN VLAN

Front 707

What command is used to define a VACL?

Back 707

vlan access-map [map-name] [sequence-number]

Front 708

What command is used to apply the VACL to VLANs.

Back 708

vlan filter [map-name] vlan-list [vlan-list]

Front 709

When a VACL is implemented on a switch, how is the switching speed affected?

Back 709

It isn’t; VACLs are implemented in hardware, so packets can be inspected as they are being switched with no performance penalty.

Front 710

What actions can be taken on packets matching a VACL?

Back 710

Packets can be forwarded, dropped, marked for capture, or redirected to a different Layer 2 switch port.

Front 711

A secondary community VLAN is associated with a primary VLAN on a switch. Can hosts
assigned to the community VLAN communicate with each other?

Back 711

Yes, they can. However, they can’t communicate with any other community or isolated VLAN.

Front 712

A secondary isolated VLAN is associated with a primary VLAN on a switch. Can hosts
assigned to the isolated VLAN communicate with each other?

Back 712

No, hosts on an isolated VLAN can’t even communicate among themselves. They can reach
only the promiscuous host on the primary VLAN.

Front 713

A router is identifed as the central gateway for a private VLAN. What command is needed to configure the switch port where a router is connected?

Back 713

switchport mode private-vlan promiscuous

Front 714

How many actual VLANs must be configured to implement a common router with two
community VLANs?

Back 714

Three VLANs must be used: one for the primary VLAN where the router is connected and two more for the secondary community VLANs. The primary VLAN will be logically associated with the two community VLANs, but all three must be configured.

Front 715

How is switching performance affected when several SPAN sessions are enabled?

Back 715

Switching performance is not affected. Packets are simply marked and copied into another
switch port’s queue during a SPAN session. The original traffic is still forwarded without being modified or affected.

Front 716

What command can specify the source of a SPAN session as VLAN 100?

Back 716

monitor session 1 source vlan 100

Front 717

When a SPAN session is enabled, what direction of traffic flow (relative to the source port) is mirrored for analysis?

Back 717

By default, traffic in both directions is mirrored.

Front 718

What must be configured on all switches connecting an RSPAN source and destination? What commands can be used?

Back 718

The special-purpose RSPAN VLAN must be configured. Define the VLAN number and then use the remote-span command.

Front 719

To configure a private VLAN, begin by defining any secondary VLANs that are needed for isolation using what two configuration commands?

Back 719

Switch(config)# vlan [vlan-id]
Switch(config-vlan)# private-vlan {isolated | community}

Front 720

You can define the primary VLAN that will provide the underlying private VLAN connectivity using what three configuration commands?

Back 720

vlan [vlan-id]
private-vlan primary
private-vlan association

Front 721

What two commands are used to associate ports with Private VLANs?

Back 721

switchport mode private-vlan {host | promiscuous}

switchport private-vlan host-association [primary-vlan-id secondaryvlan-id]

Front 722

To configure a SPAN session, start by defining the source of the SPAN session data, using what global configuration command?

Back 722

monitor session

Front 723

What two commands would define an RSPAN VLAN for
transport (all switches from sourcecto destination)?

Back 723

vlan [vlan-id]
remote-span