Friday, 15 June 2012

OSPF Areas: Totally NSSA:

OSPF Areas: Totally NSSA:

·         Totally NSSA area is a Totally-stubby-area, which has external connectivity.
·         Default-route gets injected into this by an ABR.

Network topology and Configs are same as the previous post (Stub Area).

·         In the previous NSSA post, we learnt that Type-5 LSAs are blocked in NSSA area and redistributed routes inside NSSA area will come as Type-7 LSAs.
·         These Type-7 LSAs are valid only inside NSSA area and ABR converts them into Type-5 LSAs before sending them to other areas.

Now, let’s configure Area 1 as Totally NSSA:

R2(config)#router ospf 1
R2(config-router)#area 1 nssa no-summary

If we check R3’s routing table, we shouldn’t see any External and Inter-area routes:

R3#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is to network is subnetted, 1 subnets
C is directly connected, Loopback33 is subnetted, 1 subnets
C is directly connected, Loopback0 is subnetted, 1 subnets
C is directly connected, Serial1/1 is subnetted, 1 subnets
O [110/65] via, 00:27:38, Serial1/1 is subnetted, 1 subnets
C is directly connected, Loopback133
O*IA [110/65] via, 00:01:27, Serial1/1

·         We don’t see any Inter-area routes.
·         Intra-area routes will still be there since they are local to the area.
·         We also see one default route injected into Totally NSSA area by an ABR R2.

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