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286 Cards in this Set

  • Front
  • Back
What command is used to enable and use a switch port?
no shutdown
A VLAN is what kind of domain?
A broadcast domain
Switches provide VLAN connectivity at which layer of the OSI model?
Layer 2
What is needed to pass data between two PCs, each connected to a different VLAN?
A Layer 3 process on a switch or router
Which switch command is used to assign a port to a VLAN?
switchport access vlan [vlan-id]
What is the Cisco proprietary method for trunk encapsulation?
ISL
Which protocol dynamically negotiates trunking parameters?
DTP - Dynamic Trunking Protocol
How many different VLANs can an 802.1Q trunk support?
4,096
If two switches each support all types of trunk encapsulation on a link between them, which one will be negotiated?
ISL
What is the purpose of an 802.1Q tunnel?
To transport an 802.1Q trunk across a service provider network
Which VLAN trunk encapsulation method adds a 26-byte header, a 4-byte trailer to each frame, and includes a 10-bit VLAN ID?
ISL
Which VLAN trunk encapsulation method adds a 4-byte tag; includes a 12-bit VLAN ID
802.1Q
What two commands create a VLAN and name it?
vlan [vlan-num] name [vlan-name]
What three commands assign a port to a VLAN?
interface [type module/number] switchport mode access switchport access vlan [vlan-num]
What command is used to verify VLAN configuration?
show vlan id [vlan-id]
What command is used to verify active trunk parameters?
show interface [type mod/num]trunk
What command is used to verify DTP operation?
show dtp [interface type mod/num]
Name two types of VLANs in terms of spanning areas of the campus network.
Local VLAN End-to-end VLAN
What three switch commands would configure Fast Ethernet port 4/11 for VLAN 2?
interface fastethernet 4/11 switchport mode access switchport access vlan 2
What is the default VLAN on all ports of a Catalyst switch?
VLAN 1
What methods of Ethernet VLAN frame identification can be used on a Catalyst switch trunk?
802.1Q ISL
What is the difference between the two VLAN trunking methods? How many bytes are added to trunked frames for VLAN identification in each method?
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.
What is the purpose of Dynamic Trunking Protocol (DTP)?
DTP allows negotiation of a common trunking method between endpoints of a trunk link.
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?
switchport trunk allowed vlan 100, 200-205, 300
Two neighboring switch trunk ports are set to the auto mode with ISL trunking encapsulation mode. What will the resulting trunk mode become?
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.
What is the command to configure the switch port to use DTP to actively ask the other end to become a trunk?
switchport mode dynamic desirable
Which command can set the native VLAN of a trunk port to VLAN 100 after the interface has been selected?
switchport trunk native vlan 100
What command can configure a trunk port to stop sending and receiving DTP packets completely?
switchport nonegotiate
What command can be used on a Catalyst switch to verify exactly what VLANs will be transported over trunk link gigabitethernet 4/4?
show interface gigabitethernet 4/4 switchport -OR- show interface gigabitethernet 4/4 trunk
What type of switch port must a customer present to a service provider if an IEEE 802.1Q tunnel is desired?
802.1Q trunk
A full Layer 2-only switched network is referred to as what?
a flat network topology.
What are the two VLAN membership methods exist on Cisco Catalyst switches?
static and dynamic
Which VLAN membership methods is port based?
static VLAN membership
What is the name of the VLAN database where VLAN information is automatically stored on a switch?
vlan.dat
What 3 commands are used to assign switc ports to VLANs?
Switch(config)# interface [type module/number] Switch(config-if)# switchport mode access Switch(config-if)# switchport access vlan [vlan-num]
What command outputs a list of all VLANs defined in the switch?
show vlan
What type of VLAN spans the entire switch fabric of a network?
end to end VLAN
Cisco supports trunking on what type of switch links?
Cisco supports trunking on both Fast Ethernet and Gigabit Ethernet switch links
VLAN identification can be performed using what two methods?
Inter-Switch Link (ISL) protocol and IEEE 802.1Q protocol
Which VLAN trunking method imbeds information into the frame?
802.1Q
How does ISL modify a frame?
ISL adds a 26-byte header and a 4-byte trailer to the frame.
How many bytes does ISL add to each frame?
ISL adds a total of 30 bytes to each frame
How many bytes does 802.1Q add to each frame?
802.1Q adds 4 bytes
Can a router participate in the DTP negotiation protocol?
No
Are switch ports enabled for trunking by default?
No, by default, all switch ports are non-trunking
What 5 commands are needed to set up a port as a trunk link?
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}}
Which command defines which VLANs can be trunked over the link?
switchport trunk allowed vlan
Which VLAN is the Cisco default, which carries control protocols such as CDP, VTP, and STP
VLAN 1
Which setting places a port in permanent trunking mode?
switchport mode trunk
Which switchport mode is the default for trunking?
dynamic desirable
In which switchport mode does the port actively attempt to convert the link into trunking mode?
dynamic desirable - If the far-end switch port is configured to trunk, dynamic desirable, or dynamic auto mode, trunking is successfully negotiated.
In which switchport mode does the port convert the link into trunking mode?
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.
How often are DTP frames sent out?
DTP frames are sent out every 30 seconds
What command disables DTP completely so that DTP frames are not exchanged?
switchport nonegotiate
what technique allows trunk tunneling to be accomplished across a service provider's core network without 802.1Q trunks?
Ethernet over MPLS (EoMPLS)
What command puts a switch port into the tunnel mode?
switchport mode dot1qtunnel
What command is used to verify a VLAN's configuration on a switch?
show vlan id [vlan number]
or
show vlan name [vlanname]
Which VTP modes does not allow any manual VLAN configuration changes?
client mode
How many VTP management domains can a Catalyst switch participate in?
only 1
Which command configures a Catalyst 3550 for VTP client mode?
vtp mode client
What is the purpose of VTP pruning?
to limit the extent of broadcast traffic
Which VLAN number is never eligible for VTP pruning?
VLAN 1
If a VTP server is configured for VTP version 2, what else must happen for successful VTP communication in a domain?
All other switches in the domain must be version 2 capable.
What VTP modes can a Catalyst switch be configured for?
Server, client, and transparent modes.
Does a switch in VTP transparent mode advertise its VLANs?
No
Can VLANs be created in VTP transparent mode?
Yes
Can VLANs be created in VTP client mode?
No
How many VTP management domains can a Catalyst switch participate in?
A switch can be a member of only one VTP management domain.
On a VTP server switch, identify what you can do to reset the VTP configuration revision number to 0.
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.
How can you clear the configuration revision number on a VTP client?
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.
What command would be used to make all VLANs other than 30 and 100 eligible for pruning on a trunk interface?
switchport trunk pruning vlan except 30,100
Which VLAN numbers are never eligible for VTP pruning?
VLAN 1 and VLANs 1001 to 1005.
What does the acronym VTP stand for?
VLAN Trunking Protocol
What VTP domain name is defined on a new switch with no configuration?
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.
What command will show information about the VTP configuration on a Catalyst 3550?
show vtp status
The VLAN Trunking Protocol (VTP)operates at what layer of the OSI model?
Layer 2
In how many VTP domains can a switch belong to?
A switch can belong to only one VTP domain
When a VLAN is added to a switch in a management domain, other switches are notified of the new VLAN through what?
a VTP advertisement
By default, a switch is in what VTP mode?
VTP server mode
VTP advertisements are sent as what type of frame?
multicast frames
The VTP advertisement process starts with what configuration revision number?
zero (0)
Can a VTP revision number be altered by a power cycle of the switch?
No, it is stored in NVRAM and is not altered by a power cycle of the switch
What are the three forms of VTP advertisements?
Summary advertisements Subset advertisements Advertisement requests from clients
When do VTP domain servers send summary advertisements?
every 300 seconds and every time a VLAN database change occurs.
For VLAN configuration changes, summary advertisements are followed by what?
one or more subset advertisements with more specific VLAN configuration data.
When do VTP domain servers send subset advertisements?
after a VLAN configuration change occurs.
What global configuration command is used to assign a switch to a VTP management domain?
Switch(config)# vtp domain [domain-name]
What command configures the VTP mode on a switch?
Switch(config)# vtp mode [server | client | transparent]
What is the default VTP protocol on a switch?
VTP version 1 is the default protocol on a switch.
The current VTP parameters for a management domain can be displayed with what command?
show vtp status
VTP message and error counters can be displayed with what command?
show vtp counters
VTP pruning makes more efficient use of trunk bandwidth by doing what?
by reducing unnecessary flooded traffic (broadcasts and unknown unicasts)
By default, is VTP pruning disabled or enabled on IOS-based switches?
disabled
To enable VTP pruning, use what global configuration command?
Switch(config)# vtp pruning
Does the the VTP password on one switch have to match others in the VTP domain?
Yes
If Fast Ethernet ports are bundled into an EtherChannel, what is the maximum throughput supported on a Catalyst switch?
1600 Mbps
What type of interface represents an EtherChannel as a whole?
Port-channel
The EtherChannel load-balancing method can be set how?
globally per switch
What logical operation is performed to calculate EtherChannel load balancing as a function of two addresses?
XOR
When would PagP desirable silent mode be useful?
When the switch should not expect to receive PAgP frames
Which EtherChannel mode does not send or receive any negotiation frames?
channel-group 1 mode on
Which command can be used to see the status of an EtherChannel’s links?
show etherchannel summary
How many links can be aggregated into an EtherChannel?
2-8
What are the two main benefits of an EtherChannel?
Increased bandwidth Link redundancy
Traffic between two hosts will be distributed across all links in an EtherChannel. True or false?
False
Which three methods can you use to distribute traffic in an EtherChannel?
MAC address IP address Layer 4 port
What protocols can negotiate an EtherChannel between two switches?
PAgP LACP
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?
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.
What does the acronym PAgP stand for?
Port Aggregation Protocol
Two switches should be configured to negotiate an EtherChannel. If one switch is using PAgP “auto” mode, what should the other switch use?
PAgP “desirable” mode
What interface configuration command is needed to select LACP as the EtherChannel negotiation protocol?
channel-protocol lacp
What command could you use to see the status of every port in an EtherChannel?
show etherchannel summary
What command could you use to verify the hashing algorithm used for EtherChannel load balancing?
show etherchannel load-balance
What five attributes of a set of switch ports must match to form an EtherChannel?
Port speed Port duplex Trunking mode Trunking encapsulation Access or native VLAN
What command would be used to select an EtherChannel load-balancing method for a switch?
port-channel load-balance [method]
What two commands would be used use a PAgP mode on an interface and set up an EtherChannel?
channel-protocol pagp channel-group [number] mode [on | auto | desirable]
What command is used to configure frame distribution for all EtherChannel switch links?
Switch(config)# port-channel load-balance [method]
What commandis used to verify how effective a configured load-balancing method for EtherChannel is performing?
The show etherchannel port-channel command. Each link in the channel will be displayed, along with a “Load” value.
What does LACP stand for?
Link Aggregation Control Protocol (LACP), it is a standards-based method of creating an EtherChannel
What EtherChannel mode does not send or receive PAgP or LACP packets?
on mode
What EtherChannel mode attempts to ask the far end to bring up a channel?
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.
What EtherChannel mode mode participates in the channel protocol, but only if the far end asks for participation?
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.
What command is used to verify the EtherChannel state?
show etherchannel summary
What command is used to verify the EtherChannel channel negotiation mode?
show etherchannel port
What command is used to show detailed status about each EtherChannel component?
show etherchannel detail
How is a bridging loop best described?
A loop formed between switches where frames circulate endlessly
Configuration BPDUs are originated by what?
Only the Root Bridge switch
What is the single most important design decision to be made in a network running STP?
Root Bridge placement
What happens to a port that is neither a Root Port nor a Designated Port?
It is put into the Blocking state.
What is the maximum number of Root Ports that a Catalyst switch can have?
1
What mechanism is used to set STP timer values for all switches in a network?
Configuring the timers on the Root Bridge switch.
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?
Learning
What is the default “hello” time for IEEE 802.1D?
2 seconds
If a switch has 10 VLANs defined and active, how many instances of STP will run using PVST+ versus CST?
10 for PVST+, 1 for CST
What are the five STP states?
disabled, blocking, listening, learning, forwarding
In what STP port state can a port receive BPDUs but cannot send or receive data or learn MAC addresses?
blocking
In what STP port state can a port send and receive BPDUs but cannot send or receive data or learn MAC addresses?
Listening
In what STP port state can a port send and receive BPDUs and learn MAC addresses but cannot send or receive data?
Learning
In what STP port state can a port send and receive BPDUs, learn MAC addresses, and send and receive data?
Forwarding
In spanning tree, which bridge becomes the root bridge?
Bridge with Lowest Bridge ID
In spanning tree, which port becomes the root port?(one per switch)
Port with the lowest Root Path Cost
What is the STP port path cost for 4 Mbps?
250
What is the STP port path cost for 10 Mbps?
100
What is the STP port path cost for 16 Mbps?
62
What is the STP port path cost for 45 Mbps?
39
What is the STP port path cost for 100 Mbps?
19
What is the STP port path cost for 1 Gbps?
4
What is the STP port path cost for 10 Gbps?
2
What is the default value for STP forward delay?
15 seconds
What is the default value for STP max age?
20 seconds
What is the time spent in Listening and Learning states before transitioning toward Forwarding state in STP called?
forward delay (15 seconds)
What is the maximum length of time a BPDU can be stored without receiving an update called?
max age (20 seconds)
What type of spanning tree has one instance of STP, over the native VLAN; 802.1Q-based?
CST (common spanning tree)
What type of spanning tree has one instance of STP per VLAN; Cisco ISL-based?
PVST
What type of spanning tree provides interoperability between CST and PVST; operates over both 802.1Q and ISL?
PVST+
What are two types of STP messages used to communicate between bridges?
Configuration BPDU ACK BPDU
In STP, what criteria are used to select the Root Bridge?
Lowest Bridge ID (Bridge priority, MAC address)
In STP, what criteria are used to select the Root Port?
Lowest Root Path Cost
In STP, what criteria are used to select the Designated Port?
Lowest Root Path Cost on a shared segment
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?
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.
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?
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.
What parameters can be tuned to influence the selection of a port as a Root or Designated Port?
Port Cost
Using the default STP timers, how long does it take for a port to move from the Blocking state to the Forwarding state?
30 seconds
Over what VLAN(s) does the CST form of STP run?
The native VLAN
What is the major difference between PVST and PVST+?
PVST+ interoperates with CST and PVST.
STP data messages are exchanged in the form of what?
BPDUs (bridge protocol data units)
BPDU frames have a destination address of what well-known STP multicast address?
01-80-c2-00-00-00
What two types of BPDUs exist?
Configuration BPDU, used for Spanning Tree computation and Topology Change Notification (TCN) BPDU, used to announce changes in the network topology
The Bridge ID is an 8-byte value consisting of what fields?
Bridge priority (2 bytes) and MAC address (8 bytes)
On a switch running STP, the one port that has the best path to the Root Bridge is called what?
The root port
The time interval that a switch stores a BPDU before discarding it is called what?
Max Age (20 seconds)
Default STP timer values are based on what network diameter?
7 switches
In STP, to announce a change in the active network topology, switches send out what?
TCN BPDUs (Topology Change Notification BPDUs)
Where should the Root Bridge be placed on a network?
Closest to the center of the network
What can happen as a result of a poorly placed Root Bridge in a network?
STP topology can take unexpected paths.
What should you change to make a switch become a Root Bridge?
Bridge Priority
What is the default STP Bridge Priority on a Catalyst switch?
32,768
What command can make a switch become the Root Bridge for VLAN 5, assuming that all switches have the default STP parameters?
spanning-tree vlan 5 priority 100 (something less than 32,768)
What is the default Path Cost of a Gigabit Ethernet switch port?
4
What command can change the Path Cost of interface Gigabit Ethernet 3/1 to a value of 8?
spanning-tree cost 8
What happens if the Root Bridge switch and another switch are configured with different STP hello timer values?
The other switch changes its hello timer to match the Root Bridge.
What network diameter value is the basis for the default STP timer calculations?
7
Where should the STP PortFast feature be used?
An access layer switch port connected to a PC
Where should the STP UplinkFast feature be enabled?
An access layer switch
If used, the STP BackboneFast feature should be enabled where?
all switches in the network
What command is used to enable STP?
spanning-tree [vlan-id]
What command is used to set bridge priority for STP?
spanning-tree vlan [vlan-id]priority [bridge-priority]
What command is used to set port cost for STP?
spanning-tree [vlan vlan-id] cost [cost]
What commands are used to set the three STP timers?
spanning-tree [vlan vlan-id] hello-time [seconds] spanning-tree [vlan vlan-id] forward-time [seconds] spanning-tree [vlan vlan-id] max-age [seconds]
What command is used to set PortFast on an interface?
spanning-tree portfast
What command is used to set UplinkFast on a switch?
spanning-tree uplinkfast
What command is used to set BackboneFast on a switch?
spanning-tree backbonefast
What STP timer values can be automatically modified by setting the network diameter?
Hello timer Forward Delay timer Max age timer
Which STP timer determines how long a port stays in the Listening state? What is its default value?
The Forward Delay timer; default 15 seconds
What is the purpose of the Max Age timer?
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.
What command can enable the STP PortFast feature on a switch? What configuration mode must you enter first?
spanning-tree portfast, in the interface configuration mode
To prevent STP surprises you should always do what two things?
(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.
What command is used to change the STP bridge priority for an switch?
Switch (config)# spanning-tree vlan [vlan-id] priority [bridge-priority]
What command is used to let a switch become an STP Root by automatically choosing a Bridge Priority value?
Switch(config)# spanning-tree vlan [vlan-id] root {primary | secondary}
Which STP feature enables fast connectivity to be established on access layer switch ports to workstations that are booting up?
PortFast
Which STP feature enables fast uplink failover on an access layer switch when dual uplinks are connected into the distribution layer?
UplinkFast
Which STP feature enables fast convergence in the network backbone (core) after a Spanning Tree topology change occurs?
BackboneFast
PortFast shortens what two STP states?
15 seconds Listening to Learning and 15 seconds Learning to Fowarding
What command is used to view all possible STP parameters for all VLANs and ports?
show spanning-tree
Why is it important to protect the placement of the Root Bridge?
To keep the STP topology stable
Which feature protects a switch port from accepting superior BPDUs?
STP root guard
Which command can you use to enable STP root guard on a switch port?
spanning-tree guard root
Where should the STP root guard feature be enabled on a switch?
Only ports where the Root Bridge should never appear
Whiich feature protects a switch port from accepting BPDUs when PortFast is enabled?
STP BPDU guard
Which feature can you use to identify when BPDUs are delayed as they pass through the topology?
BPDU skew detection
To maintain a loop-free STP topology, what should a switch uplink be protected against?
A sudden loss of BPDUs
What command can enable STP loop guard on a switch port?
spanning-tree guard loop
STP loop guard detects which condition?
The sudden lack of BPDUs
Which STP feature can actively test for the loss of the receive side of a link between switches?
UDLD
UDLD must detect a unidirectional link before what can happen?
STP moves the link to the forwarding state
What must a switch do when it receives a UDLD message on a link?
Echo the message back across the link.
What command is used to enable root guard on an interface?
spanning-tree guard root
What command is used to enable BPDU guard on an interface?
spanning-tree bpduguard enable
What command is used to enable loop guard on an interface?
spanning-tree guard loop
What command is used to globally enable UDLD?
udld [aggressive | enable | message time]
What command is used to look for ports that have been put in an inconsistent STP state?
show spanning-tree inconsistentports
What command is used to show UDLD status?
show udld [type mod/num]
What command is used to re-enable all ports that UDLD has errdisabled?
udld reset
Where should you apply root guard?
Apply to ports where root is never expected.
What condition must be met to keep a switch port in the blocking state?
A constant flow of BPDUs. Without them, the switch thinks there is no need to block the port any longer.
If a switch port is shown to be in the root-inconsistent state, what has happened on it?
Root guard has detected someone advertising a BPDU that is superior to the current Root Bridge.
When root guard has been triggered on a switch port, what must be done to enable the port for use again?
Root guard will automatically allow the port to be moved through the STP states as soon as the superior BPDUs are no longer received.
When BPDU guard is enabled on a switch port, what state will the port be put in if a BPDU is received on it?
errdisable
When BPDU guard has been triggered on a switch port, what must be done to enable the port for use again?
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.
What can happen if BPDUs are delayed or “skewed” as they pass along from switch to switch?
A blocking link can be moved to forwarding, creating a bridging loop, if BPDUs are delayed or dropped.
What action does BPDU skew detection take when late BPDUs are detected?
None, other than generating a syslog message to alert someone of the skewed condition.
When loop guard is enabled on a switch port, what state will the port be put in if BPDUs are noted to be missing?
loop-inconsistent
Can STP loop guard be enabled on all switch ports?
Yes; only the non-designated ports will be affected by loop guard.
When UDLD is enabled on a switch port, what else must be done to detect a unidirectional link on the port?
Enable UDLD on the far-end switch on the same link.
What is the difference between the UDLD normal and aggressive modes?
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.
What command enables UDLD aggressive mode on a switch interface?
udld aggressive
If two switches enable UDLD on the ports that have a common link, do their UDLD message times have to agree?
No. The UDLD messages are just echoed back, so the message times are only locally significant.
UDLD should be used on switch ports with what type of media?
Fiber-optic media
Can UDLD be used on all switch ports without causing problems?
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.
What command would be used to display all ports that are disabled due to STP protection features?
show spanning-tree inconsistentports
In STP, which switch port is the one port on a switch that is closest (lowest Root Path Cost) to the Root Bridge?
root port
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?
designated port
In STP, which switch ports are ports that are neither Root nor Designated Ports?
blocking ports
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?
alternate ports
In STP, which switch portds have no STP activity; these are ports with normal end user connections?
forwarding ports
The one central source of BPDUs in an STP domain is what?
The root bridge
BPDUs are regularly sent out when?
Every two seconds
Upon which standard is RSTP based?
802.1w
When a switch running RSTP receives an 802.1D BPDU, what happens?
The switch begins to use 802.1D rules on that port.
When does an RSTP switch consider a neighbor to be down?
After three BPDUs are missed
Which process is used during RSTP convergence?
Synchronization
What causes RSTP to view a port as a point-to-point port?
Port duplex
What event triggers a topology change with RSTP on a nonedge port?
A port moves to the forwarding state.
What standard defines the MST protocol?
802.1s
How many instances of STP are supported in the Cisco implementation of MST?
16
What switch command can be used to change from PVST+ to MST?
spanning-tree mode mst
What are the four RSTP port roles?
 Root Port  Designated Port  Alternate Port  Backup Port
What are the three RSTP port states?
 Discarding  Learning  Forwarding
Which STP instance involved with MST is used to maintain a single loop-free topology for the entire network?
CST (common spanning tree)
Which STP instance involved with MST is used like CST to maintain a single, loop-free topology inside an MST region?
Internal Spanning Tree (IST)
Which STP instance involved with MST is used inside an MST region to maintain loop-free topologies for sets of mapped VLANs?
MST Instances (MSTIs)
What command is used to enable MST on a switch?
spanning-tree mode mst
What command is used to enter MST configuration mode?
spanning-tree mst configuration
What command is used to name the MST region?
name [name]
What command is used to map VLANs to an MST instance?
instance [instance-id] vlan [vlan-list]
What command is used to confirm new MST configuration changes?
show pending
In RSTP, can a switch port be a Designated Port and be in the Discarding state?
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.
What two messages must be exchanged during RSTP synchronization?
Proposal and Agreement
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.)
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.
In RSTP, after a switch receives news of a topology change, how long does it wait to flush entries out of its CAM table?
The switch flushes entries immediately, rather than employing the timer reduction that 802.1D uses.
What command configures a port as an RSTP edge port?
spanning-tree portfast
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?
spanning-tree link-type point-to-point
What three parameters must be configured to uniquely define an MST region?
The region name, configuration revision number, and the instance-to-VLAN mappings
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?
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
Which MST instance in a region corresponds to the CST of 802.1Q?
The Internal Spanning Tree (IST) instance
Which MST instance is the IST?
IST is Instance 0. Instances 1 through 15 are available for other use.
When an MST region meets a PVST+ domain, how is each MST instance propagated into PVST+?
The BPDUs from each instance are replicated and sent into all the appropriate VLANs in the PVST+ switch.
Is it wise to assign VLANs to MST Instance 0? Why or why not?
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.
A switch can interact with both 802.1D and RSTP. Can it run both PVST+ and MST simultaneously?
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.
In what RSTP port state are incoming frames simply dropped; no MAC addresses are learned?
discarding
In what RSTP port state are incoming frames dropped, but MAC addresses are learned?
learning
In what RSTP port state are incoming frames forwarded according to MAC addresses that have been (and are being) learned?
forwarding
What are the three RSTP port states?
discarding learning forwarding
In RSTP, how long does it take a switch can detect a neighbor failure?
In three Hello intervals (default 6 seconds)
What are the three RSTP port types?
Edge, root and point to point
MST is built on the concept of what?
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.