Lab 51 - EIGRP Filtering with Offset-List

Prerequisites: CCNP level skills.

Note!
Use the basic EIGRP configuration (Lab 45 Task 1) in the labs 45-53.

EIGRP filtering can use:

1. Standard ACL.
2. Extended ACL.
3. Prefix-List.
4. Route-Map.
5. Administrative Distance.
6. Passive-Interface.
7. Offset-List.
8. Stub Routing.
9. Selective Stub Routing (stub routing with leak map).

Topology

Pic. 1 - Topology Diagram.

Icons designed by: Andrzej Szoblik - http://www.newo.pl

Task 1

Change the metric on R1 to prefer the next-hop 10.1.13.3 towards 172.16.103.0/24 and the next-hop 10.1.123.3 towards 172.16.133.0/24. Do not use a route-map to accomplish this.

Lab Solution


Task 1
Change the metric on R1 to prefer the next-hop 10.1.13.3 towards 172.16.103.0/24 and the next-hop 10.1.123.3 towards 172.16.133.0/24. Do not use a route-map to accomplish this.

Pic. 2 - The Current R1's Routing Table

(before a change).

Since there are three paths (also via F1/0) it is good to look at the AD of R2 which also must advertise these two prefixes. A proper adjustment must include R2 as well.

Pic. 3 - EIGRP Topology for 172.16.103.0/24 on R1.

Notice!

R2's AD equals FD through R1 (both S0/0 and S0/0). If I add the offset to the metric received from R1, R2 becomes the best path.


R1 Configuration:

!

access-list 1 permit 172.16.103.0
access-list 2 permit 172.16.133.0
access-list 3 permit 172.16.133.0
access-list 3 permit 172.16.103.0

!

router eigrp 1
 offset-list 1 in 100 Serial0/0
 offset-list 2 in 100 Serial0/1
 offset-list 3 in 300 FastEthernet1/0
 network 10.1.13.1 0.0.0.0
 network 10.1.123.1 0.0.0.0
 network 10.1.124.1 0.0.0.0
 network 172.16.101.1 0.0.0.0
 no auto-summary

!

The configuration accomplishes the goal.

Pic. 4 - The Current R1's Routing Table

(after a change).