Let’s move on to the last OSPF area type , the Not-so-totally-stubby area.
With a Not-so-totally-stubby area, type-3 Summary LSAs, type-4 ASBR Summary LSAs, and type-5 External LSAs are removed and replaced with a type-3 Summary LSA default route.
Type-7 NSSA External LSAs are allowed to be originated inside the area.
This will reduce the routing table compare to NSSA as it will suppress all the O IA routes.
To configure Not-so-totally-stubby area, I have remove the default-information-originate option on R10.
Configuration and verification:
Configuration is easy, we just had to add the no-summary command on R10.
R10(config)#router ospf 10 R10(config-router)#area 100 nssa no-summary
On R11, the routing table is drastically reduce and a default route is injected by R10.
R11#sh ip route Gateway of last resort is 10.10.101.1 to network 0.0.0.0 O*IA 0.0.0.0/0 [110/11] via 10.10.101.1, 00:43:50, Ethernet0/0 10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
R10 is still translating type 7 LSAs into type 5 LSAs.
R10# sh ip ospf 10 Routing Process "ospf 10" with ID 100.100.100.100 Start time: 00:00:22.413, Time elapsed: 04:35:29.678 SNIP Area 100 Number of interfaces in this area is 1 It is a NSSA area Perform type-7/type-5 LSA translation
And on R9, external route redistributed into OSPF on R11 are seen as OSPF external type 2.
R9# sh ip route 22.214.171.124 Routing entry for 126.96.36.199/32 Known via "ospf 10", distance 110, metric 20, type extern 2, forward metric 21 Last update from 10.10.3.10 on Ethernet0/1, 03:57:44 ago Routing Descriptor Blocks: * 10.10.3.10, from 100.100.100.100, 03:57:44 ago, via Ethernet0/1 Route metric is 20, traffic share count is 1
We have covered all the OSPF area type.
In the next post, we will work on multiple exit point when using stub areas.
Thank you for reading.
OSPF – Implement and troubleshoot area types – Not-so-totally-stubby area