Chapter 9 EIGRP – Part 2 of 2 CIS 82 Routing Protocols and Concepts Rick Graziani Cabrillo College [email protected] Last Updated: 4/20/2009

Chapter 9EIGRP – Part 2 of 2

CIS 82 Routing Protocols and Concepts

Rick Graziani

Cabrillo College

[email protected]

Last Updated: 4/20/2009

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Note My web site is www.cabrillo.edu/~rgraziani. For access to these PowerPoint presentations and other

materials, please email me at [email protected].

See notes section for additional information.

mailto:[email protected]

3

For further information This presentation is an

overview of what is covered in the curriculum/book.

For further explanation and details, please read the chapter/curriculum.

Book: Routing Protocols

and Concepts By Rick Graziani and

Allan Johnson ISBN: 1-58713-206-0 ISBN-13: 978-58713-

206-3

DUAL

DUAL Concepts Successor and Feasible Distance Feasible Successors, Feasibility Condition, and Reported Distance Topology Table: Successor and Feasible Successor Topology Table: No Feasible Successor Finite State Machine

5

DUAL Concepts Diffusing Update Algorithm is the algorithm used by EIGRP. Determines:

Best loop-free path Loop-free backup paths (which can be used immediately)

DUAL also provides the following: Fast convergence Minimum bandwidth usage with bounded updates

DUAL uses several terms that are discussed in more detail throughout this section: Successor Feasible distance Feasible successor Reported distance or advertised distance Feasible condition or feasibility condition

6

R1

R2 R3

RA

RB

RX

10.0.0.0/8

I can get to 10.0.0.0/8 with a metric of 100.


I will choose R3 to get to

10.0.0.0/8 which means I have a

cost of 120. Is R2 a valid back up?

No, because it comes back through R1 (loop).

7

R1

R2 R3

RA

RB

RX

10.0.0.0/8



I will choose R3 to get to

10.0.0.0/8 which means I have a

cost of 120. Is R2 a valid back up?

Yes, because it has its own path to 10.0.0.0/8. (no loop)

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EIGRP is a distance vector routing protocol.

Does not see any topology map. Can’t tell if there is a loop or

not? To play it safe, EIGRP only

accepts a backup route if it meets the Feasibility Condition (coming).

R1 will only use R2 if R2’s metric to 10.0.0.0/8 is less than R1’s cost through R3.

I can only use R2 as a backup

if it reports a cost less than my total cost through R3.

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Download: cis82-EIGRP-B-student.pkt Completed configuration from cis82-EIGRP-A-student.pkt

EIGRP has been configured on R1, R2 and R3 All routers have the proper bandwidth commands. Do show run

Topology

may not

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Successor and Feasible Distance

A successor is a neighboring router that is used for packet forwarding and is the least-cost route to the destination network.

What router is the success for R2? R3

R2# show ip route

<code output omitted>

D 192.168.1.0/24 [90/3014400] via 192.168.10.10, 00:00:15, S0/0/1

IP address of the successor

Successor

R3 is my successor for getting to 192.168.1.0/24

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Successor and Feasible Distance

Feasible distance (FD) is the lowest calculated metric to reach the destination network. The metric for the route.

R2# show ip route

<code output omitted>

D 192.168.1.0/24 [90/3014400] via 192.168.10.10, 00:00:15, S0/0/1

Feasible Distance

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Feasible Successors, Feasibility Condition, and Reported Distance

DUAL fast convergence because it can use backup paths to other routers known as feasible successors. Does not require to recompute DUAL.

SuccessorFeasible Successor?

I wonder if R1 could be a feasible successor for getting

to 192.168.1.0/24?

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Feasible Successors, Feasibility Condition, and Reported Distance

Is R1 a Feasible Successor? Does R2 know if R1 has a loop-free backup path to 192.168.1.0/24? Remember, EIGRP is a Distance Vector Routing protocol.


I wonder if R1 could be a feasible successor for getting

to 192.168.1.0/24?

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Feasible Successor

A feasible successor (FS) is a neighbor who has a loop-free backup path to the same network as the successor by satisfying the feasibility condition.

Would R2 consider R1 to be a feasible successor to network 192.168.1.0/24?

To be a feasible successor, R1 must satisfy the feasibility condition (FC).

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The reported distance (advertised distance) - EIGRP neighbor’s FD to the same destination network. The metric that a router reports to a neighbor about its own cost to that

network. Feasibility Condition: The FC is met when a neighbor’s reported distance

(RD) to a network is less than the local router’s FD to the same destination network.

R1# show ip route

<output omitted>

D 192.168.1.0/24 [90/2172416] via 192.168.10.6, 01:12:26, Serial0/0/1

Feasibility Condition

My FD to 192.168.1.0/24

is 2,172,416 (my routing

table).

I will send R2 my RD to

192.168.1.0/24 of 2,172,416.

Feasibility Condition: For R1 to be a Feasible Successor it must tell me that it’s metric to

reach 192.168.1.0/24 is less than my metric

through my Successor R3.

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If R3 is the successor, can the neighbor R1 be a Feasible Successor to this same 192.161.0/24 network? In other words, if the link between R2 and R3 fails, can R1 immediately

be used as a backup path without a recomputation of DUAL? R1 can only be an FS (Feasible Successor) if it meets the FC (Feasibility

Condition).



Feasibility Condition: For R1 to be a Feasible

Successor it must tell me that it’s metric to reach

192.168.1.0/24 is less than my metric through my

Successor R3.

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R1’s FD to 192.168.1.0/24 is 2,172,416. R1 reports 2,172,416 to R2 as its RD (Reported Distance) R2’s perspective: 2,172,416 is?

R1’s RD (Reported Distance) to 192.168.1.0/24 R1’s perspective: 2,172,416 is?

Its FD (Feasible Distance) to 192.168.1.0/24

R1# show ip route

<output omitted>

D 192.168.1.0/24 [90/2172416] via 192.168.10.6, 01:12:26, Serial0/0/1


My FD to 192.168.1.0/24

is 2,172,416 (my routing

table).

I will send R2 my RD to

192.168.1.0/24 of 2,172,416.

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Does R1 meet the Feasibility Condition? Is the RD of R1, 2,172,416, less than R2’s own FD of 3,014,400? Yes, R1 meets the feasibility condition.

R1 is a FS (Feasible Successor) for R2 to the 192.168.1.0/24 network.

R1# show ip route

<output omitted>

D 192.168.1.0/24 [90/2172416] via 192.168.10.6, 01:12:26, Serial0/0/1

R2# show ip route

<output omitted>

D 192.168.1.0/24 [90/3014400] via 192.168.10.10, 00:00:15, Serial0/0/1

R1’s RD is less than R2’s FD, so R1 is the FS for 192.168.1.0/24

Feasibility Condition: For R1 to be a Feasible Successor it must tell me that it’s metric to reach

192.168.1.0/24 (Reported Distance) is less than my metric (Feasible Distance) through my

Successor R3.

Feasible Distance

Reported Distance sent to R2

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Why isn’t R1 the successor if its RD is less than R2’s FD to 192.168.1.0/24? The 64 Kbps link would be used as the “slowest bandwidth part of the

metric calculation. The total cost for R2, its FD to reach 192.168.1.0/24 is greater through R1

41,026.560 than it is through R3 3,014,400.

R1# show ip route

<output omitted>

D 192.168.1.0/24 [90/2172416] via 192.168.10.6, 01:12:26, Serial0/0/1

R2# show ip route

<output omitted>

D 192.168.1.0/24 [90/3014400] via 192.168.10.10, 00:00:15, Serial0/0/1

If R1 was the successor, the 64 Kbps link is the slowest bandwidth, plus another delay of R1’s s0/0/1. This would be a higher metric (41,026.560) than 3,014,400 via successor R3.

Feasible Distance

Reported Distance sent to R2

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Topology Table: Successor and Feasible Successor

The successor, FD, and any FSs with their RDs are kept by a router in its EIGRP topology table or topology database.

Do on R2: show ip eigrp topology Can you find the successor and feasible successor for

192.168.1.0/24?

R2# show ip eigrp topology

IP-EIGRP Topology Table for AS(1)/ID(10.1.1.1)

Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,

r - reply Status, s - sia Status

<output omitted>

P 192.168.1.0/24, 1 successors, FD is 3014400

via 192.168.10.10 (3014400/28160), Serial0/0/1

via 172.16.3.1 (41026560/2172416), Serial0/0/0


via Connected, Serial0/1

<output omitted>

Feasible Successor

Successor

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Topology Table: Successor and Feasible Successor

P: This route is in the Passive state. DUAL is not performing its diffusing computations to determine a path for a

network The route is in a stable mode Active state - DUAL is recalculating or searching for a new path

192.168.1.0/24: This is the destination network that is also found in the routing table.

How many successors are there? What does it mean? 1 successors: This shows the number of successors for this network.

If there are multiple equal-cost paths to this network, there will be multiple successors.

FD is 3014400: This is the FD, the EIGRP metric to reach the destination network.

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via 192.168.10.10: This is the next-hop address of the successor, R3. This address is shown in the routing table.

3,014,400: This is the FD to 192.168.1.0/24. It is the metric shown in the routing table.

28,160: This is the RD of the successor R3’s cost to reach this network.

Serial0/0/1: This is the outbound interface used to reach this network. Also shown in the routing table.

Successor Information

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via 172.16.3.1: This is the next-hop address of the FS, R1. 41,026,560: This would be R2’s new FD to 192.168.1.0/24 if R1 became the

new successor. 2,172,416: This is the RD of the FS or R1’s metric to reach this network.

This value, RD, must be less than the current FD of 3,014,400 to meet the FC.

Serial0/0/0: This is the outbound interface used to reach the FC, if this router becomes the successor.

Feasible Successor Information

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Show eigrp topology [network]R2# show ip eigrp topology 192.168.1.0

IP-EIGRP topology entry for 192.168.1.0/24

State is Passive, Query origin flag is 1, 1 Successor(s), FD is 3014400

Routing Descriptor Blocks:

192.168.10.10 (Serial0/0/1), from 192.168.10.10, Send flag is 0x0

Composite metric is (3014400/28160), Route is Internal

Vector metric:

Minimum bandwidth is 1024 Kbit

Total delay is 20100 microseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1500

Hop count is 1

172.16.3.1 (Serial0/0/0), from 172.16.3.1, Send flag is 0x0

Composite metric is (41026560/2172416), Route is Internal

Vector metric:

Minimum bandwidth is 64 Kbit

Total delay is 40100 microseconds

Reliability is 255/255

Load is 1/255

Minimum MTU is 1500

Hop count is 2

Successor

Feasible Successor

Default metrics calculations

Optional metrics

Other information passed in routing update (not part of composite metric)

Reported Distance of R1 to R2 for 192.168.1.0

Feasible Distance for to 192.168.1.0 if R3 was the successor. This is the metric that would be if R2’s routing table if R3 was the successor.

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What if the link between R2 and R3 failed?

R2# show ip route

<output omitted>

D 192.168.1.0/24 [90/3014400] via 192.168.10.10, 00:00:15, Serial0/0/1

Feasible DistanceR2# show ip route

<output omitted>

D 192.168.1.0/24 [90/41026560] via 192.168.10.10, 00:00:15, Serial0/0/1

X

SuccessorFeasible SuccessorSuccessor

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Topology Table: No Feasible Successor

Route to 192.168.1.0/24: What router is the Successor for 192.168.10.6?

R3 What is R1’s FD?

2,172,416

R1# show ip route

192.168.10.0/24 is variably subnetted, 3 subnets, 2 masks

D 192.168.10.0/24 is a summary, 00:45:09, Null0

C 192.168.10.4/30 is directly connected, Serial0/0/1

D 192.168.10.8/30 [90/3523840] via 192.168.10.6, 00:44:56, S0/0/1



C 172.16.1.0/24 is directly connected, FastEthernet0/0

D 172.16.2.0/24 [90/40514560] via 172.16.3.2, 00:45:09, S0/0/0


D 192.168.1.0/24 [90/2172416] via 192.168.10.6, 00:44:55, S0/0/1

Successor

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Is R2 a Feasible Successor? If current path to 192.168.1.0/24 fails will R1 (DUAL) automatically use R2 as

a backup route? Is the path to 192.168.1.0/24 via R2 a guaranteed loop-free path? (more later) Does R2 meet the Feasibility Condition?

Feasible Successor?

R1# show ip route

D 192.168.1.0/24 [90/2172416] via 192.168.10.6, 00:44:55, S0/0/1


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Does the topology table only any Feasible Successors? No, only the successor.

Why do you think R2 is not a Feasible Successor? R2 is not an FS because it does not meet the FC.

Topology shows that R2 has a backup route EIGRP does not have a map of the network topology. EIGRP is a distance vector routing protocol

Feasible Successor?



<output omitted>


via 192.168.10.6 (2172416/28160), Serial0/0/1

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You can view all possible links whether they satisfy the feasible condition or not by adding the [all-links] option. Even those routes that are not FSs.

Is R2 a Feasible Successor? Does R2 meet the Feasibility Condition? Is R2’s RD less than R1’s FD?

R1# show ip eigrp topology all-links

<output omitted>

P 192.168.1.0/24, 1 successors, FD is 2172416, serno 5

via 192.168.10.6 (2172416/28160), Serial0/0/1

via 172.16.3.2 (41026560/3014400), Serial0/0/0

<output omitted>Feasible Successor? (No)

Successor

R1’s FD

R2’s RD

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Even though R2 looks like a viable backup path to 192.168.1.0/24, R1 has no idea that its path is not a potential loop back through itself.

R2 does not meet FC!

R2’s RD 3,014,400 > R1’s FD 2,172,416

Feasible Successor?


<output omitted>


via 192.168.10.6 (2172416/28160), Serial0/0/1

via 172.16.3.2 (41026560/3014400), Serial0/0/0

<output omitted>

R1’s FD

R2’s RD

My FD is 3,014,400. I will

send this as my RD to R1.

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Does this mean R2 cannot be used if the successor fails? R2 can be used, but there will be a longer delay before adding it

to the routing table. Before this can happen, DUAL will need to do some further

processing, which is explained in the next topic.


R2 does not meet FC!

R2’s RD 3,014,400 > R1’s FD 2,172,416

Feasible Successor?

My FD is 3,014,400. I will

send this as my RD to R1.


<output omitted>


via 192.168.10.6 (2172416/28160), Serial0/0/1

via 172.16.3.2 (41026560/3014400), Serial0/0/0

<output omitted>

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The centerpiece of EIGRP is DUAL (EIGRP route-calculation engine). DUAL Finite State Machine (FSM)

This FSM contains all the logic used to calculate and compare routes in an EIGRP network.

Finite State Machine

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DUAL FSM

FSMs defines: The set of possible states that something can go through What events cause those states What events result from those states

Beyond the scope of this course.

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HUNGRY(START)

FOOD ISINEDIBLE

GET FOOD

FULL

EAT ENOUGHFOOD

NOT ENOUGHFOOD

NO FOODFOR 5

HOURS

EAT MOREFOOD EATING

FSM Example

35

DUAL FSM


<partial output>


via 192.168.10.10 (3014400/28160), Serial0/0/1

via 172.16.3.1 (41026560/2172416), Serial0/0/0

SuccessorFeasible Successor

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DUAL FSM

shutdown command simulates a failure of the link between R2 and R3.

R2# debug eigrp fsm

R2# conf t

R2(config)# int s0/0/1

R2(config-if)# shutdown

<some debug output omitted>

DUAL: Find FS for dest 192.168.1.0/24. FD is 3014400, RD is 3014400

DUAL: 192.168.10.10 metric 4294967295/4294967295

DUAL: 172.16.3.1 metric 41026560/2172416 found Dmin is 41026560

DUAL: Removing dest 192.168.1.0/24, nexthop 192.168.10.10

DUAL: RT installed 192.168.1.0/24 via 172.16.3.1

X

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DUAL FSM

R1 now becomes the successor There are no new feasible successors.

R2# show ip route

<some output omitted>

D 192.168.1.0/24 [90/41026560] via 172.16.3.1, 00:08:58, Serial0/0


<partial output>


via 172.16.3.1 (41026560/2172416), Serial0/0

Previous topology table

Successor

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No Feasible Successor

What if the path to the successor fails and there are no FSs? R1 to 192.168.1.0/24

R3 is the Successor No Feasible Successors

NOT Feasible Successor

Successor

39


Simulate a failure of the link between R1 and R3 with a shutdown on R1’s S0/0/1 interface.


<output omitted>


via 192.168.10.6 (2172416/28160), Serial0/0/1

<output omitted>

NOT Feasible Successor

SuccessorX

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192.168.1.0/24 network put into the active state and shows that EIGRP queries are sent to other neighbors.

R2 replies with a path to this network This becomes the new successor Installed into the routing table.

R1# debug eigrp fsm

R1# conf t


R1(config-if)# shutdown

<some debug output omitted>

DUAL: Find FS for dest 192.168.1.0/24. FD is 2172416, RD is 2172416

DUAL: 192.168.10.6 metric 4294967295/4294967295

DUAL: 172.16.3.2 metric 41026560/3014400 not found Dmin is 41026560

DUAL: Dest 192.168.1.0/24 entering active state.

DUAL: rcvreply: 192.168.1.0/24 via 172.16.3.2 metric 41026560/3014400

DUAL: Find FS for dest 192.168.1.0/24. FD is 4294967295, RD is 4294967295 found

DUAL: Removing dest 192.168.1.0/24, nexthop 192.168.10.6

DUAL: RT installed 192.168.1.0/24 via 172.16.3.2

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R1# show ip route

<some output omitted>

D 192.168.1.0/24 [90/41026560] via 172.16.3.2, 00:00:17, Serial0/0/0

SuccessorX

1. R1 puts 192.168.1.0/24 into Active State.

2. Query from R1 for 192.168.1.0/24

3. R2 forwards the Query for 192.168.1.0/24

4. R3 replies to R2 – Yes I have a route to 192.168.1.0/24

5. R2 forwards the reply to R1

6. R1 puts route to 192.168.1.0/24 via R2 into Routing Table.

Successor

This process takes longer than if R1 had R2 as Feasible Successor in it’s topology table.

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The topology table for R1 now shows R2 as the successor and shows that there are no new feasible successors.


<parital output>


via 172.16.3.2 (41026560/3014400), Serial0/0/0Successor

X

Successor

More EIGRP Configurations

The Null0 Summary Route Disabling Automatic Summarization Manual Summarization EIGRP Default Route Fine-Tuning EIGRP

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The Null0 Summary Route

EIGRP automatically includes a Null0 summary route as a child route whenever both of the following conditions exist: There is at least one subnet that was learned via EIGRP. Automatic summarization is enabled. (By default with EIGRP)

What if R1 received a packet: 172.16.4.10 It would be discarded – never looking for a supernet or default route Regardless of ip classless or no ip classless command

R1# show ip route




D 192.168.10.8/30 [90/3523840] via 192.168.10.6, 00:44:56, S0/0/1




D 172.16.2.0/24 [90/40514560] via 172.16.3.2, 00:45:09, S0/0/0


D 192.168.1.0/24 [90/2172416] via 192.168.10.6, 00:44:55, Serial0/0/1

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Disabling Automatic Summarization

Like RIP, EIGRP automatically summarizes at major network boundaries using the default auto-summary command.

R3# show ip route





D 172.16.0.0/16 [90/2172416] via 192.168.10.5, 01:08:30, Serial0/0/0


172.16.0.0/16

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Both R1 and R2 automatically summarizing. R1 is the successor because of the difference in bandwidth.

R3# show ip route





D 172.16.0.0/16 [90/2172416] via 192.168.10.5, 01:08:30, Serial0/0/0


172.16.0.0/16

172.16.0.0/16

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Is this the best route for all 172.16.0.0 subnets? No R3 will route all packets destined for 172.16.2.0 through R1.

Solution? Need R1 and R2 to send individual subnets. R1 and R2 must stop automatically summarizing 172.16.0.0/16.

R3# show ip route

<output omitted>

D 172.16.0.0/16 [90/2172416] via 192.168.10.5, 01:08:30, Serial0/0/0

172.16.0.0/16

48


Automatic summarization can be disabled with the no auto-summary. The router configuration command eigrp log-neighborchanges is on by

default on some IOS implementations. .

R1(config)# router eigrp 1

R1(config-router)# no auto-summary

%DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 172.16.3.2 (Serial0/0/0) is resync: summary configured

%DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 172.16.3.2 (Serial0/0/0) is down: peer restarted

%DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 172.16.3.2 (Serial0/0/0) is up: new adjacency

<output omitted>





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R1 no more Null0 summary routes:


D 172.16.0.0/16 is a summary, 00:46:10, Null0 What does this mean?

This mean any packets for their parent networks that do not match a child route, the routing table will check supernet and default routes.

Unless no ip classess is used

R1# show ip route

192.168.10.0/30 is subnetted, 2 subnets

C 192.168.10.4 is directly connected, Serial0/0/1

D 192.168.10.8 [90/3523840] via 192.168.10.6, 00:16:55, S0/0/1



D 172.16.2.0/24 [90/3526400] via 192.168.10.6, 00:16:53, S0/0/1


D 192.168.1.0/24 [90/2172416] via 192.168.10.6, 00:16:52, Serial0/0/1


50

R2 no more Null0 summary routes :



R2# show ip route


D 192.168.10.4 [90/3523840] via 192.168.10.10, 00:15:44, S0/0/1



D 172.16.1.0/24 [90/3526400] via 192.168.10.10, 00:15:44, S0/0/1




C 10.1.1.0 is directly connected, Loopback1

D 192.168.1.0/24 [90/3014400] via 192.168.10.10, 00:15:44, S0/0/1


51

Why does R3’s routing table now have two equal-cost paths to 172.16.3.0/24? Shouldn’t the best path only be through R1 with the 1544-Mbps link?

R3# show ip route





D 172.16.1.0/24 [90/2172416] via 192.168.10.5, 00:00:11, S0/0/0

D 172.16.2.0/24 [90/3014400] via 192.168.10.9, 00:00:12, S0/0/1

D 172.16.3.0/30 [90/41024000] via 192.168.10.5, 00:00:12, S0/0/0

[90/41024000] via 192.168.10.9, 00:00:12, S0/0/1


172.16.0.0/16

172.16.0.0/16

52


The slowest link is the 64-Kbps link

R3# show ip route

<output omitted>

D 172.16.3.0/30 [90/41024000] via 192.168.10.5, 00:00:12, S0/0/0

[90/41024000] via 192.168.10.9, 00:00:12, S0/0/1

172.16.0.0/16

172.16.0.0/16

53

Manual Summarization

EIGRP can be configured to summarize routes, whether or not automatic summarization (auto-summary) is enabled.

Modified topology.

54


Add two more networks to R3. Configure EIGRP network statements.

R3(config)# interface loopback 2

R3(config-if)# ip address 192.168.2.1 255.255.255.0

R3(config-if)# interface loopback 3

R3(config-if)# ip address 192.168.3.1 255.255.255.0

R3(config-if)# router eigrp 1

R3(config-router)# network 192.168.2.0

R3(config-router)# network 192.168.3.0

55


Instead of sending three separate networks, R3 can summarize the 192.168.1.0/24, 192.168.2.0/24, and 192.168.3.0/24 networks as a single route.

R1# show ip route

D 192.168.1.0/24 [90/2172416] via 192.168.10.6, 02:07:38, S0/0/1

D 192.168.2.0/24 [90/2297856] via 192.168.10.6, 00:00:34, S0/0/1

D 192.168.3.0/24 [90/2297856] via 192.168.10.6, 00:00:18, S0/0/1

R2# show ip route

D 192.168.1.0/24 [90/3014400] via 192.168.10.10, 02:08:50, S0/0/1

D 192.168.2.0/24 [90/3139840] via 192.168.10.10, 00:01:46, S0/0/1

D 192.168.3.0/24 [90/3139840] via 192.168.10.10, 00:01:30, S0/0/1

Only pertinent routes shown

192.168.1.0/24, 192.168.2.0/24,

192.168.3.0/24 192.168.1.0/24, 192.168.2.0/24,

192.168.3.0/24

56

Determining the Summary EIGRP Route

1. Write out the networks that you want to summarize in binary.2. Find the matching bits.

Count the number of leftmost matching bits, which in this example is 22. This number becomes your subnet mask for the summarized route: /22

or 255.255.252.0.3. To find the network address for summarization, copy the matching 22 bits

and add all 0 bits to the end to make 32 bits.

The result is the summary network address and mask for 192.168.0.0/22

57

Configure EIGRP Manual Summarization

Because R3 has two EIGRP neighbors, the EIGRP manual summarization in configured on both Serial 0/0/0 and Serial 0/0/1.

Router(config-if)# ip summary-address eigrp as-number network-address subnet-mask

R3(config)# interface serial 0/0/0

R3(config-if)# ip summary-address eigrp 1 192.168.0.0 255.255.252.0


R3(config-if)# ip summary-address eigrp 1 192.168.0.0 255.255.252.0

192.168.0.0/22

192.168.0.0/22

58

Verify EIGRP Manual Summarization

Fewer number of total routes in routing tables Faster routing table lookup process more efficient.

Summary routes also require less bandwidth Single route can be sent rather than multiple individual routes.

R1# show ip route

<output omitted>

D 192.168.0.0/22 [90/2172416] via 192.168.10.6, 00:01:11, Serial0/0/1

R2# show ip route

<output omitted>

D 192.168.0.0/22 [90/3014400] via 192.168.10.10, 00:00:23, Serial0/0/1

192.168.0.0/22

192.168.0.0/22

59

EIGRP Default Route

R2(config)# ip route 0.0.0.0 0.0.0.0 loopback 1


R2(config-router)# redistribute static

The ISP router in our topology does not physically exist. By using a loopback interface, we can simulate a connection to another router.

Default RouteRedistribute default static route in EIGRP updates

60

EIGRP Default Route

R1# show ip route

Gateway of last resort is 192.168.10.6 to network 0.0.0.0

D*EX 0.0.0.0/0 [170/3651840] via 192.168.10.6, 00:02:14, S0/0/1

R2# show ip route


S* 0.0.0.0/0 is directly connected, Loopback1

R3# show ip route


D*EX 0.0.0.0/0 [170/3139840] via 192.168.10.9, 00:01:25, S0/0/1

Only static default route shown, other output omitted.


61

EIGRP Default Route

R1# show ip route


D*EX 0.0.0.0/0 [170/3651840] via 192.168.10.6, 00:02:14, S0/0/1

Only static default route shown, other output omitted.

D: This static route was learned from an EIGRP routing update. *: The route is a candidate for a default route. EX: The route is an external EIGRP route, in this case a static route outside

of the EIGRP routing domain. 170: This is the AD of an external EIGRP route.


62

EIGRP Default Route

There is another method to propagate a default route in EIGRP, using the ip default-network command.

More information on this command can be found at this site: http://www.cisco.com/en/US/tech/tk365/

technologies_tech_note09186a0080094374.shtml.


63

Fine-Tuning EIGRP: EIGRP Bandwidth Utilization

By default, EIGRP uses only up to 50 percent of the bandwidth of an interface for EIGRP information.

Prevents the EIGRP process from overutilizing a link. Can be modified with ip bandwidth-percent eigrp

Router(config-if)# ip bandwidth-percent eigrp as-number percent

EIGRP updates use no more than 50% of the link’s bandwidth by default.

64

EIGRP Bandwidth Utilization

Limit EIGRP to no more than 25 percent of the link’s bandwidth. EIGRP will never use more the 18 Kbps of the link’s bandwidth for

EIGRP packet traffic.


R1(config-if)# bandwidth 64

R1(config-if)# ip bandwidth-percent eigrp 1 25


R2(config-if)# bandwidth 64

R2(config-if)# ip bandwidth-percent eigrp 1 25

65

Configuring Hello Intervals and Hold Times

Hello intervals and hold times do not have to match with other EIGRP routers to establish adjacencies. We will see later, OSPF’s Hello and other timers do need to

match. Range from 1 to 65,535

If you change the hello interval, make sure that you also change the hold time to a value greater than the hello interval.

Otherwise, neighbor adjacency will go down after the hold time expires and before the next hello interval.

Router(config-if)# ip hello-interval eigrp as-number seconds

Router(config-if)# ip hold-time eigrp as-number seconds

66

Configuring Hello Intervals and Hold Times

The no form can be used on both of these commands to restore the default values.


R1(config-if)# ip hello-interval eigrp 1 60

R1(config-if)# ip hold-time eigrp 1 180


R2(config-if)# ip hello-interval eigrp 1 60

R2(config-if)# ip hold-time eigrp 1 180

67

Topics Introduction to EIGRP

EIGRP: An Enhanced Distance Vector Routing Protocol

EIGRP Message Format Protocol-Dependent Modules RTP and EIGRP Packet Types Hello Protocol EIGRP Bounded Updates DUAL: An Introduction Administrative Distance Authentication

Basic EIGRP Configuration EIGRP Network Topology Autonomous Systems and

Process IDs The router eigrp Command The network Command Verifying EIGRP Examining the Routing Table

EIGRP Metric Calculation EIGRP Composite Metric and the K

Values EIGRP Metrics Using the bandwidth Command Calculating the EIGRP Metric

DUAL DUAL Concepts Successor and Feasible Distance Feasible Successors, Feasibility

Condition, and Reported Distance Topology Table: Successor and

Feasible Successor Topology Table: No Feasible

Successor Finite State Machine

More EIGRP Configurations The Null0 Summary Route Disabling Automatic Summarization Manual Summarization EIGRP Default Route Fine-Tuning EIGRP

Chapter 9EIGRP

CIS 82 Routing Protocols and Concepts

Rick Graziani

Cabrillo College

[email protected]

Last Updated: 4/28/2008

Documents

Chapter 9 EIGRP – Part 2 of 2 CIS 82 Routing Protocols and Concepts Rick Graziani Cabrillo College [email protected] Last Updated: 4/20/2009