Lab 52 - EIGRP Filtering with Stub Routing

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

Add two more loopbacks on R4 with the respective addresses:
Loopback 2: 10.0.4.4/24
Loopback 3: 10.0.44.4/24

Advertise them as External prefixes.

Task 2
Configure R4 so that it can advertise only connected and summary routes in EIGRP. It should not be queried by R1 and/or R2 if they lose any EIGRP prefix.

Lab Solution

Task 1

Add two more loopbacks on R4 with the respective addresses:

Loopback 2: 10.0.4.4/24

Loopback 3: 10.0.44.4/24

Advertise them as External prefixes.

R4 Configuration:

!

interface Loopback2
 ip address 10.0.4.4 255.255.255.0
!
interface Loopback3
 ip address 10.0.44.4 255.255.255.0
!
route-map CONNECTED permit 10
 match interface Loopback2 Loopback3
!

router eigrp 1
 redistribute connected route-map CONNECTED
 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

!

Verification:

Pic. 2 - R3 Receives External Prefixes.

Task 2

Configure R4 so that it can advertise only connected and summary routes in EIGRP. It should not be queried by R1 and/or R2 if they lose any EIGRP prefix.

R4 Configuration:

!

router eigrp 1
 redistribute connected route-map CONNECTED
 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

 eigrp stub connected summary

!

Pic. 3 - EIGRP Stub Options (the defaults in yellow).

Verification:

Pic. 4 - R1 Sees R4 as the Stub Router.

R4 can now only advertise directly connected networks/subnets (these enabled in EIGRP) as well as summary route (the defaults in 'stub' command). Also R1 and R2 are not going to send EIGRP Query packets upon losing their EIGRP prefixes.

Note!
Even though R4 is a 'stub' router allowing connected and summary routes, it does advertise EIGRP prefixes that have been redistributed. They are still connected enabled (redistributed) in EIGRP. 

Pic. 5 - R3's External Prefixes.