Cisco

Front 1

Name the hello timers on EIGRP?

Back 1

5 seconds on fast links.
60 seconds on slow (<T1) links.

Front 2

Name the hold down timers on EIGRP?

Back 2

By default 3 times the hello, which means: 15 seconds on fast links, and 180 seconds on slow (<T1) links.

Front 3

What is the SRTT?

Back 3

Smooth Round Trip Timer. A cisco proprietary way of calculating the actual time from a router to a router and back.

Front 4

What is the RTO (Eigrp)?

Back 4

Its a Retransmission Timeout timer. It is the amount of time between unicast retransmissions.

Front 5

How are timers used between neighbors in EIGRP?

Back 5

Each router transmit the timer it EXPECTS. That means that if R1 sends a certain hello and a holddown timer, this is what it expects from the neighbor. The neighbor will then use that hold down timer in its adjacency with R1.

Front 6

What has to match for an EIGRP adjacency to form?

Back 6

K-values must match and the neighbor must be within the subnet of the receiving interface. (Not exact same as in OSPF).

Front 7

How many equal cost paths can by default be installed by EIGRP into the RIB?

Back 7

By default 4.

Front 8

How many equal cost paths can MAX be installed by EIGRP into the RIB?

Back 8

16 Paths.

Front 9

What happens if you issue a "clear ip route *" when using EIGRP?

Back 9

The routing table is repopulated through the EIGRP topology table. It will not change what paths it choose in the first place. No queries are sent, and no routes go active.

Front 10

How do you change the number of paths EIGRP install into the route table?

Back 10

"max-paths <number>" where number is any number between 1-16.

Front 11

EIGRP's way of balancing across multiple paths are determined how?

Back 11

Three ways to do so: 1) Balanced, 2) No traffic share, 3) Minimum.
Balanced distributes data according to their metric. No traffic share uses all paths equally. Minimum only use the path with the lowest metric.

Front 12

How can you stop an adjacency from forming on a specific interface?

Back 12

"passive-interface <if>" under the EIGRP process. This will stop hello's from being sent on the interface, thereby stopping adjacencies.

Front 13

How do you install feassible successor routes into the RIB even though they are not equal to the current successor?

Back 13

"variance <multiplier>" command. This command multiplies the current metric of the successor. If any feassible successor routes fall within this range they are also installed into the RIB. The FS FD must be less or equal to FD of Successor route.

Front 14

Default setting for split-horizon in EIGRP?

Back 14

Default on all interfaces. Use point-to-point interface on frame-relay to overcome this.

Front 15

Name the different times and their values in RIP?

Back 15

Update timer, Hold-down timer, Invalid timer, Flush timer.
Update: 30 seconds, used to send updates (full) on this interval. Hold-down, 180 seconds when receiving a bad route (16), stop accepting any route-update for this route in this amount of time.

When no update has been received in the invalid-timer (180 seconds), it is set to invalid, and Metric=16 are sent out to all, including the one it learned it from (poison reverse).

Finally the flush timer is 240 seconds, after which the route is removed from the routing table.

Front 16

Where is split-horizon enabled by RIP?

Back 16

All interfaces except frame-relay physical interfaces.

Front 17

What types of authentication does RIPv2 support?

Back 17

Plaintext or MD5.

Front 18

How does RIPv2 handle autosummarization?

Back 18

RIPv2 summarizes all routes at a major net boundary (even routes received from other neighbors).

Front 19

Explain EIGRP autosummarization?

Back 19

EIGRP will autosummarize (if it is on) by a major network boundary, but it must be a connected route advertised with the network command. Routes received by another neighbor are not summarized.

Front 20

What is the main difference between IGMPv1 and IGMPv2?

Back 20

The main purpose of making a version 2 was to improve leave latency by implementing a leave command.

Front 21

How is a querier elected in IGMPv1?

Back 21

IGMPv1 does not elect a querier. It relies on L3 Multicast protocols to elect a DR. Whoever wins this election becomes the querier.

Front 22

What role does IGMP have in a network?

Back 22

IGMP is the Internet Group Management Protocol. It handles end user multicast requests. Makes sure that routing protocols will route to this lan.

Front 23

How is an IGMP querier elected?

Back 23

An IGMP querier is in Version 1 the same as the one PIM elects as the DR for the lan. Highest IP wins. In IGMP version 2, the lowest IP wins the querier election.

Front 24

What is a DR in a PIM multicast network?

Back 24

A designated router is selected. This is the one that sends joins toward either the source or the RP on behalf of clients.

Front 25

What are assert messages?

Back 25

Assert messages are used when multiple routers send data onto a segment. Each of them figures this out, and sends an assert message. The one with the best AD, metric and then highest IP to the source wins. The other routers stop forwarding traffic onto the lan to stop multiple flows.

Front 26

Explain PIM-DM.

Back 26

PIM-DM is based on the premises that all segments wants data. It then pushes this data out, and expects everyone that doesnt want it to prune it.

Front 27

How are (*,G) entries used in IOS?

Back 27

Everytime a multicast routes exists, there is always a (*,G). Normally in Shared Trees, this would point toward the RP. In PIM-DM it just lists the PIM neighbors, and is used for a better structure in IOS.

In PIM-SM this always points to the RP.

Front 28

What is a (S,G) entry?

Back 28

It is an entry that points toward the source, hence being a SPT entry.

Front 29

Explain the usage of RPF?

Back 29

Reverse Path Forwarding. Is used to figure out the best path toward the source of the data. Is used to make sure no routing loops exists. If multiple equal cost links exists toward the source (or RP), use the one with the highest IP address.

Front 30

Explain PIM?

Back 30

Protocol Independent Multicast. Based on the fact that it uses the normal unicast routing table.
It creates adjacencies like other routing protocols. Hello's are sent every 30 seconds.
Hold-down time is normally 3xhello time.
Uses the multicast address of 224.0.0.13.

Front 31

Explain the multicast mapping from IP to Mac address.

Back 31

The address 01005e is always used in the mac-address as the first 24 bits. That leaves 24 bits for the rest of the MAC address.The lowest 23 bits are mapped directly into this, and 0 is the 24th bit. IP multicast addresses always start with 1110 (224). This means that 32 different IP addresses map to the same MAC address.

The reason behind this, is that all multicast addresses start with 1110, that leaves 28 bits. Since we only map the lower 23 bits, we have 5 bits remaining (2^5 = 32).

Front 32

Name the different ways to configure IPv6

Back 32

Stateful autoconfiguration, assigns a complete 128 bit address.
Stateless autoconfiguration, gives out the prefix and the EUI is added.
EUI-64, prefix is determined by the administrator, and the last 64bits with the EUI mechanism.

Front 33

What is EUI-64?

Back 33

It is a way to form the host part of an IPv6 address. This is the last 64 bits. Uses the MAC address and inserts FFFE in the middle. The 7th bit in the interface ID must be set to 1 to indicate a unique global address.

Front 34

What is autosummarization?

Back 34

A feature of routing protocols to automatically summarize on classfull network boundaries.
RIP does it everywhere when configured. EIGRP must have an EIGRP connected route before it will summarize.
BGP can also autosummarize.

If RIP, if the route to be advertised has the same major net as the interface advertising it, if it has the same mask, it will be advertised with this mask. If not it will be dropped. If it is not part of the same major net, it will be summarized to the classfull net.

Front 35

Name the frame-relay encapsulation types available?

Back 35

Cisco and IETF.

Front 36

Name the frame-relay LMI types.

Back 36

Cisco, Ansi, Q.933a.

Front 37

What does LMI do?

Back 37

Gives information about the PVC's configured.

Front 38

Given this command, what type of LSA are sent into the area?
"area 1 nssa default-information originate"

Back 38

Contrary to normal stub area, a default route is not inserted automatically. A surprising result is that the default-information originate, will insert a type 7 0.0.0.0 route into the nssa area.

Front 39

Given a type 2 LSA, what does the Link ID mean?

Back 39

It is the interface address of the DR on a multiaccess network (type 2).

Front 40

Given a type 2 LSA, what does the Advertising Router mean?

Back 40

It is the router-id of the DR.

Front 41

What is the multicast flow timer?

Back 41

Amount of time a router will wait for an ACK (after sending multicast) before sending unicast update.

Front 42

In EIGRP how many equal cost routes can by default be installed into the routing table? (or unequal if variance is used)

Back 42

4 Routes. Up to 16 Maximum.

Front 43

How is split horizon in effect on the routing protocols?

Back 43

Eigrp = All interfaces.
RIP = All but physical frame-relay interfaces.

Front 44

What transport layer protocol and port does Syslog use?

Back 44

UDP port 514

Front 45

Account for the usage of "bgp deterministic-med".

Back 45

When enabled, routes from the same AS are grouped together. The one with the best MED in each group is then compared against each other. But NOT compared according to MED.

Front 46

Account for the usage of "bgp always-compare med"

Back 46

When enabled alone, MED is always taken into the path selection.

Front 47

Account for the usage of both "bgp deterministic-med" and "bgp always-compare med" commands.

Back 47

When enabled, AS routes are grouped together. Winner of each group is then compared against the winner of the other groups, and it IS compared with MED taken into account.

Front 48

What command will allow a router to reflect FECN messages to BECN messages so the sender can slow down?

Back 48

"shape fecn-adapt"

Front 49

When a BECN is received, by how much is the rate slowed down?

Back 49

25% by default.

Front 50

Can WRED be implemented inbound?

Back 50

No, only outbound (to avoid sending congestion).

Front 51

What does WRED primarily stop?

Back 51

TCP global synchronization.

Front 52

What is the MPD in WRED?

Back 52

Mean Probability Denominator.
1/x bytes are dropped at MAX in a WRED profile.
So if the MPD is 10, 1/10, one in every 10 packets are dropped.

Front 53

Whats the default, IP Prec or DSCP for random-detect (WRED)?

Back 53

IP Precedence.

Front 54

What actions is taken by UDLD in normal mode when UDLD messages are not received?

Back 54

A syslog message is generated, but the port is NOT put into the err-disabled state.

The port will be put into an undetermined state.

Front 55

What action is taken by UDLD in aggressive mode?

Back 55

The port is put into the err-disabled state after not getting 8 consecutive UDLD messages.

Front 56

On what ports should loopguard be enabled and why?

Back 56

On all root and non-designated ports. These are the ports that will create a topology change. A root port might start sending out BPDU's. A non-designated port might erroneously go into the forwarding state. Loopguard prevents this. Loopguard puts the ports not receiving BPDU's into a loop-inconsistent state, until BPDU's are received again.
It does not work with root guard.

Front 57

Whats the default values for traffic-shaping? (Bc, Be, Tc)...

Back 57

If less than 320Kbps Bc 8000 bits, Be = Bc and Tc = Bc/Shaping rate.

If more than 320Kbps.
Bc = Shaping-rate * Tc, Be = Bc, and Tc is 25ms.

Front 58

How do you enable frame-relay traffic-shaping?

Back 58

The command "frame-relay traffic-shaping" must be on the interface.

Front 59

State the command to traffic-shape to 64000bps using frame-relay traffic-shaping.

Back 59

Create a map-class, use the command: "frame-relay traffic-rate 64000", put the map-class on the VC: "frame-relay class <map-class>"

Front 60

What types of default routes does RIP support?

Back 60

Default-information originate, redistribution of static routes, ip default-network.

Front 61

What types of default network injection does EIGRP support?

Back 61

Redistribution of static routes, ip default-network, summaries.

Front 62

What types of default network injection does OSPF support?

Back 62

Only default-information originate.

Front 63

What does the frame-relay status of inactive mean?

Back 63

It means that the frame-relay switch provided PVC info, but the router has not used it.

Front 64

What does the frame-relay status of active mean?

Back 64

Everything is working between the frame-relay switch and the router.

Front 65

What does the frame-relay status of deleted mean?

Back 65

The frame-relay switch is not offering the PVC anymore even though the router has been using it.

Front 66

In IGMPv2, when hosts sends a a Leave Message, what destination address is it sent to?

Back 66

224.0.0.2 - To inform all routers that it wants to leave.

Front 67

Solicited Membership Reports are sent to what address?

Back 67

To the destination address they want to receive traffic for. For example, a router sends a general query, the host responds with a membership report by sending it to that group address.

Front 68

How often are general queries sent by the router in IGMPv2?

Back 68

Every 125 seconds.

Front 69

How are Leave messages handled by the router?

Back 69

When a host sends a leave, the router sends out group specific queries. If a host responds with a membership report, nothing changes. If no reports are heard within the Last Member Query Interval (Set to MRT), for three times Last Member Query Count, data is cut off. This will normally happen within 3 seconds.

Front 70

In IGMPv2, how is the querier for the lan selected?

Back 70

Lowest IP address.

Front 71

Whats the default query interval for IGMPv2?

Back 71

125 seconds.

Front 72

Where does the RP-Bit originate?

Back 72

It originates at the point where the SPT and RPT diverge. (Different RPF neighbor).

Front 73

In HSRP, you can have routers in what states?

Back 73

1 router in active, 1 in standby, and the rest are in listen mode.

Front 74

How is speed negotiated on ethernet segments?

Back 74

Speed can be autosensed by sending Link Pulse signals. So speed can always be negotiated.

Front 75

What happens when a 10Mbit and a 100Mbit tries to negotiate?

Back 75

It will settle on 10Mbit full-duplex.

Front 76

If one end of the link is a 10Mbit interface, and is manually set to full-duplex and the other end is 100Mbit and autonegotiates, what will the end result be?

Back 76

For 10 and 100Mbit interfaces, the default duplex is half if it cant be negotiated. So the end result will be 10Mbit half-duplex.

Front 77

What is the default duplex on a 1000Mbit interface?

Back 77

Full duplex.

Front 78

What is the max-age timer used for in STP?

Back 78

It is used for detecting when any topology change occurs. After not hearing any BPDU's for this time, the port tries to change.

Front 79

in RSTP how does the switch detect that the neighbor switch is dead?

Back 79

By missing 3 BPDU's (sent every 2 seconds), it will figure out the switch is dead in 6 seconds.

Front 80

What is backbone-fast?

Back 80

It is an enhancement to 802.1D that skips the max-age on a switch. If a switch hears an inferior BPDU on a blocking port, it can send out RLQ on its non-designated ports, to figure out if it still has a path to the root-bridge. If so, it skips the max-age setting and puts the port into listening + learning states.

Front 81

When sending labels in an MPLS network, what does the label 1 and 3 mean?

Back 81

1 is TDP and 3 is LDP.

Front 82

What are the different BGP packet types?

Back 82

Open.
Update Packet.
Informational.
Keepalive.

Front 83

List the BGP path selection.

Back 83

Weight. Local preference. Self-originated. AS-path. Origin. MED.

Front 84

How is the LDP ID established?

Back 84

Either by manually configured RID, or then by the same process as OSPF. The router-id must be reachable from the neighbor. If a loopback is used, it must be a /32.

Front 85

What is the transport address in LDP?

Back 85

It is the address that neighbors use to establish a TCP connection.

Front 86

Who initiated a TCP session between LDP peers?

Back 86

The highest IP.

Front 87

What transport protocol and port is used by LDP?

Back 87

TCP port 646.

Front 88

Which tunneling technique features sites with the 2002::/16 prefix?

Back 88

6to4 tunnels.

Front 89

What IPv6 tunnel technique should be used for interconnecting IPv6 Islands?

Back 89

6to4 tunnels.

Front 90

Name the different types of "guards" in spanning-tree? and what action they will take when triggered.

Back 90

- Root guard = Err-inconsistent.
- BPDU guard = Err-disabled.
- Loop guard = Loop-inconsistent.

Front 91

What port/transport protocol is used for LDP hellos?

Back 91

646 UDP.

Front 92

Does root guard bring the interface back up when superior BPDU's cease?

Back 92

Yes.

Front 93

What does the command: "mls qos cos 7" do?

Back 93

By itself, it does nothing at all. If the command: "mls qos trust cos" is also used, packets already marked are not touched. Other packets have the cos value 7 set.

If the "mls qos cos override" is used, cos value 7 is set on all packets. (ofcourse trunk links).

Front 94

What does the command: "mls qos trust dscp" mean?

Back 94

Packets comming into this interface with dscp marked, will be trusted and not modified. It is however possible that the cos value will be modified because of the DSCP-to-CoS map.

Front 95

What is FREEK? and how is it used, what channels is it used on and what modes are available?

Back 95

FREEK = Frame-relay end-to-end keepalive. It is used on datachannels instead of LMI (0 for Q933a and Ansi, 1023 for Cisco).

It can run as bidirectional, request, reply, reply-passive.

Front 96

How do you disable timestamps on debug messages?

Back 96

"no service timestamps debug" in global config mode.

Front 97

In order to create an RSPAN, what must be put onto the vlan?

Back 97

"remote-span" on the vlan itself (not the SVI).

Front 98

how do you enable sending snmp traps to an NMS?

Back 98

"snmp-server host <ip> community> <what-traps>"
+
"snmp-server enable traps <what-traps>"

Front 99

How do you log to a local file on flash, while also limit the usage?

Back 99

"logging file flash:<file> <max-file-size> <severity>"

Front 100

What order of preference does PBR take in regard to next-hop ip?

Back 100

Next-hop IP, next-hop ip recursive, interface, next-hop default ip, default interface.

Front 101

How and by what means can you check if the next hop is available?

Back 101

"ip next-hop verify-availability" or "ip default next-hop verify-availability".

This function uses CDP to check the next hop. So the next hop has to be a Cisco device, and CDP must be enabled on the device.

Front 102

How do you check what protocol, if any, is used to establish a port-channel?

Back 102

"sh etherchannel protocol"

Front 103

What are the requirements for using private vlans?

Back 103

VTP mode MUST be transparent.

Front 104

How do you define a primary vlan?

Back 104

vlan <vlan number>
private-vlan primary

Front 105

How do you define a secondary vlan?

Back 105

vlan <vlan>
private-vlan <community|isolated>

Front 106

How do you define a host port for private vlans?

Back 106

int <interface>
switchport mode private-vlan host
switchport private-vlan host-association <primary vlan> <secondary vlan>

Front 107

How do you define a promiscous port for private vlans?

Back 107

int <interface>
switchport mode private-vlan promiscious
switchport private-vlan mapping <primary> <secondary>

Front 108

How do you use an SVI as a promiscious port?

Back 108

int <svi>
private-vlan mapping <secondary vlans>

Front 109

Whats the cisco proprietary protocol for port-channels, and what modes does it use?

Back 109

It is PAgP, and it uses auto and desirable, where auto is passive, waiting to hear from desirable.

Front 110

What port-channel mode uses active/passive states?

Back 110

LACP = industry standard. Also known as 802.3ad

Front 111

How can you view lacp/pagp protocol details?

Back 111

"sh etherchannel protocols"

Front 112

Using advertise-maps in BGP. Can you use extended access-lists to match routes?

Back 112

From testing, it appears you can use extended ACL's when matching on WHAT route to advertise, NOT the conditional route.