Note!
Use topology Lab14. OSPF should be enabled on all interfaces with the most specific wildcard mask.
Topology
Task 1
On R1 create a new loopback interface with the IP address 192.168.1.1/24. Advertise this network in OSPF as external prefix. Make sure that no other interfaces created in the future will get advertised.
Task 2
On R5 create a new loopback interface with IP address 192.168.5.5/24. Advertise this network as external E2 into OSPF domain.
Task 3
Configure routers in the area 1 so they do not accept any external and inter-area prefixes. Routers in area 1 must be able to reach the newly created networks. Routers in area 2 should be able to reach these networks as well.
Task 1
R1 Configuration:
interface Loopback1
ip address 192.168.1.1 255.255.255.0
!
match interface Loopback1
!
router ospf 1
router-id 1.1.1.1
log-adjacency-changes
redistribute connected subnets route-map CONNECTED
network 10.1.12.1 0.0.0.0 area 0
network 10.1.13.1 0.0.0.0 area 1
network 172.16.101.1 0.0.0.0 area 0
Verification:
Task 2
On R5 create a new loopback interface with IP address 192.168.5.5/24. Advertise this network as external E2 into OSPF domain.
R5 Configuration:
ip address 192.168.5.5 255.255.255.0
router-id 5.5.5.5
log-adjacency-changes
redistribute connected subnets
network 10.1.35.5 0.0.0.0 area 1
network 172.16.105.5 0.0.0.0 area 1
Verification:
Task 3
Note!
Area 1 must filter LSA5 but also introduces external prefixes (192.168.5.0/24, 192.168.5.0/24). Area 1 CANNOT be configured as totally stubby area then. NSSA totally stub area is the solution. ABR will inject a default route into area that is NSSA totally stubby area (default behavior).
R1 Configuration:
router-id 1.1.1.1
log-adjacency-changes
area 1 nssa no-summary
redistribute connected subnets route-map CONNECTED
network 10.1.12.1 0.0.0.0 area 0
network 10.1.13.1 0.0.0.0 area 1
network 172.16.101.1 0.0.0.0 area 0
R3 Configuration:
router-id 3.3.3.3
log-adjacency-changes
area 1 nssa
network 0.0.0.0 255.255.255.255 area 1
R5 Configuration:
router-id 5.5.5.5
log-adjacency-changes
area 1 nssa
redistribute connected subnets
network 10.1.35.5 0.0.0.0 area 1
network 172.16.105.5 0.0.0.0 area 1
Verification:
External and Inter-Area prefixes are gone (no E2 or 0 IA).
