Lab 19 - OSPF External Prefix Filtering

Prerequisites: CCNP level skills.

Topology and configuration as per initial configuration in the lab 18.

Topology

Pic. 1 - OSPF Multi-Area.

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

Task 1
Configure all routers according to the topology diagram. Make area 13 NSSA area. 

Task 2

On R3 create two new loopback interfaces:

• Loopback 1 = 192.168.3.3 255.255.255.0
• Loopback 2 = 192.168.33.3 255.255.255.0

Task 3

Redistribute both networks (loopback 1 and loopback 2) into OSPF.

Task 4

Creating filtering so R2 does not have 192.168.33.0/24 in its routing table. Do not filter out 192.168.3.0/24.

Lab Solution

Task 1

Configure all routers according to the topology diagram. Make area 13 NSSA area.

R1 OSPF Configuration:

!

router ospf 1
 router-id 1.1.1.1
 log-adjacency-changes
 area 13 nssa
 network 10.1.12.1 0.0.0.0 area 0
 network 10.1.13.1 0.0.0.0 area 13
 network 172.16.101.1 0.0.0.0 area 0

!

R2 OSPF Configuration:

!

router ospf 1
 router-id 2.2.2.2
 log-adjacency-changes
 network 10.1.12.2 0.0.0.0 area 0
 network 172.16.102.2 0.0.0.0 area 0
!

R3 OSPF Configuration:

!

router ospf 1
 router-id 3.3.3.3
 log-adjacency-changes
 area 13 nssa
 network 10.1.13.3 0.0.0.0 area 13
 network 172.16.103.3 0.0.0.0 area 13

!

Task 2

On R3 create two new loopback interfaces:

• Loopback 1 = 192.168.3.3/24
• Loopback 2 = 192.168.33.3/24

R3 Configuration:

!

interface Loopback1
 ip address 192.168.3.3 255.255.255.0
!
interface Loopback2
 ip address 192.168.33.3 255.255.255.0
!

Task 3

Redistribute both networks (loopback 1 and loopback 2) into OSPF.

R3 Configuration:

!

router ospf 1
 router-id 3.3.3.3
 log-adjacency-changes
 area 13 nssa
 redistribute connected subnets
 network 10.1.13.3 0.0.0.0 area 13
 network 172.16.103.3 0.0.0.0 area 13

!

Verification:

Pic. 2 - R2's Routing Table.

Task 4

Creating filtering so R2 does not have 192.168.33.0/24 in its routing table. R2's routing table must still have 192.168.3.0/24 entry.

R1 Configuration:

!

router ospf 1
 router-id 1.1.1.1
 log-adjacency-changes
 area 13 nssa
 summary-address 192.168.33.0 255.255.255.0 not-advertise
 network 10.1.12.1 0.0.0.0 area 0
 network 10.1.13.1 0.0.0.0 area 13
 network 172.16.101.1 0.0.0.0 area 0

!

Verification:

Pic. 3 - R2 Routing Table After Filtering on R1.