Saturday, March 12, 2011

Lesson 45 - EIGRP Fundamentals Part 3 - The Lab

In this post I'll put the pieces together in the practice lab. Our topology will be as presented below:

Pic. 1 - Topology Diagram.
Icons designed by: Andrzej Szoblik - http://www.newo.pl

This post is going to collect bits and pieces from lessons 43 and 44 to show you the implementation on the command line interface with verification steps.

Task List

General requirements
  • All routers must use Autonomous System 1.
  • All networks/subnets must be advertised and reachable.
  • EIGRP authentication should be enabled between R1 and R4.
  1. Enable EIGRP between R1, R2 and R3. Make sure loopbacks are advertised. Use the most specific wildcard mask.
  2. Enable EIGRP between R1 and R4. Make sure loopbacks are advertised. Use the most specific wildcard mask on R1. On R4 the network statement should be classful (no wildcard mask).
  3. Enable EIGRP between R2 and R5. Make sure loopbacks are advertised. Use the most specific wildcard mask on R2. On R5 the network statement should be classful (no wildcard mask).
  4. Enable EIGRP authentication between R1 and R4. Use the password 'cisco'.

Lab Solution

Step 1
Enable EIGRP between R1, R2 and R3. Make sure loopbacks are advertised. Use the most specific wildcard mask.

Note!
The 'no auto-summary' keyword is not necessary in my topology, but I include it to show you how to disable automatic summarization to the class boundary.
R1 Configuration:
!
R1(config)#router eigrp 1
R1(config-router)#no auto-summary
R1(config-router)#network 172.31.123.1 0.0.0.0
R1(config-router)#network 172.31.1.1 0.0.0.0
R1(config-router)#
!

R2 Configuration:
!
R2(config)#router eigrp 1
R2(config-router)#no auto-summary
R2(config-router)#network 172.31.2.1 0.0.0.0
R2(config-router)#network 172.31.123.2 0.0.0.0
R2(config-router)#
!



Pic. 2 - EIGRP Adjacency Between R1 and R3.


R3 Configuration:
!
R3(config)#router eigrp 1
R3(config-router)#no auto-summary
R3(config-router)#network 172.31.3.1 0.0.0.0
R3(config-router)#network 172.31.3.17 0.0.0.0
R3(config-router)#network 172.31.123.3 0.0.0.0
R3(config-router)#
!

Verification:
Pic. 3 - R3's EIGRP-enabled nterfaces.
Pic. 3 confirms the network statement was correct for each interface.

Pic. 4 - R3's EIGRP Neighbor Table.

Notice!
R3 heard EIGRP hello packets from two neighbors. But to be sure they have exchanged their topology tables, the 'Q Cnt' column must show '0' messages pending (not acknowledged).

Notice!
In the 'output explanation' I show only the most relevant pieces of information. Others are either self-explanatory or not necessary to understand at the CCNA level.

Output Explanation:
  • H - Handle; shows order in which the neighbors were discovered and adjacency built between them.
  • Address - The IP address of the neighbor.
  • Interface - The  local interface where neighbors are discovered.
  • Hold - Length of time in seconds how long the router is going to wait for hello packet before declaring the neighbor down.
  • Uptime - Elapsed time since the local router first heard from the neighbor.
  • SRRT - Smooth Round Trip Timer; amount of time in milliseconds the required to send the packet to the neighbor and receive the acknowledgement.
  • RTO - Retransmit Time Out; amount of time in milliseconds the local router waits before retransmitting EIGRP packet if acknowledgement did not arrive.
  • Q Cnt - The number of EIGRP packets (update, query, reply) that the router keeps in the queue to be sent. Typically, it implies that some EIGRP reliable packets have not been acknowledged.
Pic. 5 - R3's EIGRP Topology Table.

Output Explanation:
  • P - Route is Passive which means that router is not actively looking for a path towards it. It is a required status in stable topology.
  • FD - Feasible Distance (metric value towards the destination)
  • (156160/128256) - The first number (156160) is FD, the second number (128256) is the Advertised Distance advertised by the neighbor (FD of the neighbor). Recall, the Feasibility Condition from the previous lessons.
Pic. 6 - R3's Routing Table.

Output Explanation:
  • D - EIGRP learned prefix; 'show ip route' shows all prefixes including connected networks with explanation of codes.
  • [90/156160] - The first number (90) is the Administrative Distance (trustworthiness) of the protocol, the second number (156160) is the metric based on best FD from the topology table.
  • via 172.31.2.1 - next-hop router (neighbor that advertised it).
  • 00:30:04 - how long ago the prefix was learned.
  • FastEthernet1/0 - The outbound interface towards the destination.
Pic. 7 - R3's EIGRP Details.
Your homework:
look at pic. 7 and consult my previous posts about EIGRP and the topology diagram to understand the highlighted parts.

Step 2
Enable EIGRP between R1 and R4. Make sure loopbacks are advertised. Use the most specific wildcard mask on R1. On R4 the network statement should be classful (no wildcard mask).

R1 Configuration:
!
R1(config-router)#network 172.31.14.1 0.0.0.0
R1(config-router)#
!

R4 Configuration:
!
R4(config)#router eigrp 1
R4(config-router)#no auto-summary
R4(config-router)#network 172.31.0.0
R4(config-router)#network 192.168.4.0
R4(config-router)#
!


Verification should be performed after this step (look at step 1).

Step 3
Enable EIGRP between R2 and R5. Make sure loopbacks are advertised. Use the most specific wildcard mask on R2. On R5 the network statement should be classful (no wildcard mask).

R2 Configuration:
!
R2(config-router)#network 172.31.25.2 0.0.0.0
R2(config-router)#
!


R5 Configuration:
!
R5(config)#router eigrp 1
R5(config-router)#no auto-summary
R5(config-router)#network 192.168.5.0
R5(config-router)#network 172.31.0.0
R5(config-router)#
!


Verification should be performed after this step (look at step 1).

Step 4
Enable EIGRP authentication between R1 and R4. Use the password 'cisco'.

R1 Configuration:
!
R1(config)#key chain MY_EIGRP_KEY
R1(config-keychain)#key 1
R1(config-keychain-key)#key-string cisco
R1(config-keychain-key)#
R1(config-keychain-key)#int s0/2
R1(config-if)#ip authentication key-chain eigrp 1 MY_EIGRP_KEY
R1(config-if)#ip authentication mode eigrp 1 md5
!


R4 Configuration (without prompts):
!
key chain MY_EIGRP_KEY
 key 1
   key-string cisco
!
interface Serial0/2
 ip address 172.31.14.4 255.255.255.0
 ip authentication mode eigrp 1 md5
 ip authentication key-chain eigrp 1 MY_EIGRP_KEY
!


Verification:
Pic. 8 - R1's Neighbors.

R1 and R4 have re-established neighbor relationships.

In the next post, I'll present a few troubleshooting techniques based on the topology and configuration used in this lesson.

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