Lab 59 - EIGRP Router ID

Prerequisites: CCNP level skills.

Topology

Pic. 1 - Topology Diagram.

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

Note!
EIGRP adds the router ID to the external prefixes. In case the advertising router receives them back with its own ID, the are being rejected. This serves as the loop prevention mechanism.

Task1
Configure R3 with the router ID = 3.3.3.3. Advertise Loopback0 (172.16.103.0/24) and Loopback1 (172.16.133.0/24) as EIGRP external prefixes.

Task 2
Configure R4 to reject the EIGRP external prefixes advertised by R3. Do not use any filtering commands such as ACLs, route-maps, distribute-list or offset-list.

Lab Solution


Task1

Configure R3 with the router ID = 3.3.3.3. Advertise Loopback0 (172.16.103.0/24) and Loopback1 (172.16.133.0/24) as EIGRP external prefixes.

R3 Configuration:

!

route-map CONN_TO_EIGRP permit 10
 match interface Loopback0 Loopback1

!

router eigrp 1
 redistribute connected route-map CONN_TO_EIGRP
 network 10.1.13.3 0.0.0.0
 network 10.1.123.3 0.0.0.0
 no auto-summary

 eigrp router-id 3.3.3.3

!

Verification:

Pic. 4 - R4's Routing Table.

Task 2

Configure R4 to reject the EIGRP external prefixes advertised by R3. Do not use any filtering commands such as ACLs, route-maps, distribute-list or offset-list.

Pic. 3 - R3's Router ID Check on R4.

R4 Configuration:

!

router eigrp 1
 network 10.1.124.4 0.0.0.0
 network 172.16.104.4 0.0.0.0
 network 172.16.144.4 0.0.0.0
 no auto-summary
 eigrp router-id 3.3.3.3

!

Verification:

Pic. 4 - R4's Routing Table.

Notice!
R4 rejects EX prefixes this time since it has the SAME EIGRP router ID.