Cisco Route - Eigrp, Set 3

Front 1

What are the EIGRP rules for adding load-balancing routes?

Back 1

1. Routes must be a successor or feasible succesor
2. FS successor routes where metric <= current FD * variance
3. maximum-paths allows more paths

Front 2

What is the purpose of EIGRP route filtering?

Back 2

1. Prevent some (perhaps branch office or stub) routers from routing packets from one part to the network to another.
2. Reduce size of routing tables

Front 3

What are the IOS commands and mode for three different ways of implementing EIGRP route filtering?

Back 3

router configuration mode.
1. #distribute-list <acl> { in | out } [interface]
2. #distribute-list prefix <name> { in | out }
3. #distribute-list route-map <name> { in | out }
Note: for the ACL option, if interface is not supplied, the list applies to the router.

Front 4

What components of an IP route can be mached by a prefix-list?

Back 4

1. The route prefix (subnet)
2. The prefix length (mask)

Front 5

What is the command to create a prefix list?

Back 5

#ip prefix-list <name> [seq <number>]
{deny | permit <prefix>/<len>}
[ge <n>] [le <n>]

Front 6

What must be true for a prefix list to match a route?

Back 6

1. route's prefix must be in range implied by list's prefix/length
2. route's prefix length must fall within list's range

Front 7

What are the four rules for matching the prefix-length of a prefix-list?

Back 7

1. if neither ge or le, then conf-len = route-len
2. if both ge and le, then ge <= route-len <= le
3. if only le, then conf-len <= rout-len <= le
4. if only ge, then ge <= route-len <= 32

Front 8

What is the syntax of a route-map?

Back 8

#route-map <name> { permit | deny } [<seq-num>].
#match <criteria>

Front 9

What is the default result of a route-map if none of the criteria match? How do you change the default behavior?

Back 9

1. implied deny at end
2. Add a permit statement at end with no match criteria

Front 10

What does a route-map do when a permit condition is matched?

Back 10

Route is allowed through

Front 11

What does a route-map do when a deny condition is matched?

Back 11

Route is filtered

Front 12

What does a route-map do when it uses an ACL or prefix-list for matching?

Back 12

If the result is "permit", the match is successful.
If the result is "deny", the match is unsuccessful and it passes to the next statement.

Front 13

How do you verify a route-map?

Back 13

#show route-map <name>

Front 14

On which routers does EIGRP allow route summarization? How is this different than OSPF?

Back 14

EIGRP allows summarization at any router.
OSPF, allows summarization only at area border routers and autonomous system border routers.

Front 15

What are four benefits of route summarization?

Back 15

1. smaller routing tables
2. Reduces query scope
3. Summarization supported at any point in network (EIGRP)
4. Summary has metric of the best of the subnets being sumarized

Front 16

What are two tradeoffs of route summarization?

Back 16

1. May cause suboptimal routing
2. Packets destined for inaccessible destinations will flow to the summarizing router before being dropped.

Front 17

What is the mode and command to configure EIGRP route summarization?

Back 17

config-interface mode
#ip summary-address eigrp <asn> <prefix> <subnet-mask>

Front 18

When an EIGRP summary route is configured on an interface, what 4 steps does the router take?

Back 18

1. Brings down and back up all neighbor relationships on that interface, thus flushing topology data.
2. Advertises a summary route, assuming the router has at least one route in the summary range.
3. Does not advertise the subordinate (summarized) routes
4. Adds a route to its own routing table for the summary prefix/length with outgoing interface null0

Front 19

Define auto-summarization.

Back 19

When a router has multiple working interfaces using IP addresses in different classful networks, the router advertises a summary route for each classful network on interfaces attached to a different classful network.

Front 20

What is the mode and command to turn off auto-summarization for EIGRP?

Back 20

router config mode
#no auto-summary

Front 21

In what condition must you turn of auto-summarization for EIGRP?

Back 21

Discontiguous networks. Packets sent between at least one pair of subnets pass through a subnet of a different classful network.

Front 22

What are two options for EIGRP to advertise default routes?

Back 22

1. Define and advertise a static route
2. Flag an existing route to be the default route

Front 23

What are the commands to advertise a default static route in EIGRP?

Back 23

1. Create a static route: #ip route 0.0.0.0 0.0.0.0 <interface>
2. Inject the static route into EIGRP topology database: #network 0.0.0.0
or redistribute the static route.

Front 24

What are the commands to flag a route to be the default route?

Back 24

1. On the "gateway" router, define a classful network to advertise into EIGRP using the #network command. Tthis network is either configured on the outgoing interface or created on a loopback interface.
2. Configure that network as the default network: #ip default-network <network>

Front 25

Define auto-summarization.

Back 25

When a router has multiple working interfaces using IP addresses in different classful networks, the router advertises a summary route for each classful network on interfaces attached to a different classful network.

Front 26

What is the mode and command to turn off auto-summarization for EIGRP?

Back 26

router config mode
#no auto-summary

Front 27

In what condition must you turn of auto-summarization for EIGRP?

Back 27

Discontiguous networks. Packets sent between at least one pair of subnets pass through a subnet of a different classful network.

Front 28

What are two options for EIGRP to advertise default routes?

Back 28

1. Define and advertise a static route
2. Flag an existing route to be the default route

Front 29

What are the commands to advertise a default static route in EIGRP?

Back 29

1. Create a static route: #ip route 0.0.0.0 0.0.0.0 <interface>
2. Inject the static route into EIGRP topology database: #network 0.0.0.0
or redistribute the static route.

Front 30

What are the commands to flag a route to be the default route?

Back 30

1. On the "gateway" router, define a classful network to advertise into EIGRP using the #network command. Tthis network is either configured on the outgoing interface or created on a loopback interface.
2. Configure that network as the default network: #ip default-network <network>

Front 31

What stub keywords are used by default, if no keywords are specified?

Back 31

connected and static

Front 32

What type of packet does an EIGRP router send in response to a HELLO packet?

Back 32

An UPDATE packet.

Front 33

Which routes (successors and/or feasible successors) will be shown by the #show ip route eigrp command?

Back 33

Just the successors. Need to use #show ip eigrp topology to see the feasible successors.