ABR in Stub area not blocking External Routes

jskfan
jskfan used Ask the Experts™
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ABR in Stub area not blocking External Routes
ar
In the topology above I have configured R2 area 1 as stub the same for R3
R3 is blocking External Routes E2 and injecting IA default routes, but R2 is still allowing E2 [External routes]

R2#sh run | sec ospf
router ospf 1
 area 1 stub
 network 192.168.12.0 0.0.0.255 area 0
 network 192.168.23.0 0.0.0.255 area 1
R2#

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R3#sh run | sec ospf
router ospf 1
 area 1 stub
 network 192.168.23.0 0.0.0.255 area 1
R3#

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R2#sh ip route ospf
Codes: L - local, 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, H - NHRP, l - LISP
       a - application route
       + - replicated route, % - next hop override

Gateway of last resort is not set

      7.0.0.0/32 is subnetted, 1 subnets
O E2     7.7.7.7 [110/20] via 192.168.12.1, 00:41:55, Ethernet0/0
      9.0.0.0/32 is subnetted, 1 subnets
O E2     9.9.9.9 [110/20] via 192.168.12.1, 00:41:55, Ethernet0/0
      11.0.0.0/32 is subnetted, 1 subnets
O E2     11.11.11.11 [110/20] via 192.168.12.1, 00:41:55, Ethernet0/0
O     192.168.14.0/24 [110/20] via 192.168.12.1, 00:41:55, Ethernet0/0
O     192.168.16.0/24 [110/20] via 192.168.12.1, 00:41:55, Ethernet0/0
O     192.168.18.0/24 [110/20] via 192.168.12.1, 00:41:55, Ethernet0/0
O IA  192.168.45.0/24 [110/30] via 192.168.12.1, 00:41:55, Ethernet0/0
O IA  192.168.67.0/24 [110/30] via 192.168.12.1, 00:41:55, Ethernet0/0
O IA  192.168.89.0/24 [110/30] via 192.168.12.1, 00:41:55, Ethernet0/0
O     192.168.110.0/24 [110/20] via 192.168.12.1, 00:41:55, Ethernet0/0
O IA  192.168.111.0/24 [110/30] via 192.168.12.1, 00:41:55, Ethernet0/0
O     192.168.112.0/24 [110/20] via 192.168.12.1, 00:41:55, Ethernet0/0
R2#

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R3#sh ip route ospf
Codes: L - local, 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, H - NHRP, l - LISP
       a - application route
       + - replicated route, % - next hop override

Gateway of last resort is 192.168.23.2 to network 0.0.0.0

O*IA  0.0.0.0/0 [110/11] via 192.168.23.2, 00:06:26, Ethernet0/0
O IA  192.168.12.0/24 [110/20] via 192.168.23.2, 00:06:26, Ethernet0/0
O IA  192.168.14.0/24 [110/30] via 192.168.23.2, 00:06:26, Ethernet0/0
O IA  192.168.16.0/24 [110/30] via 192.168.23.2, 00:06:26, Ethernet0/0
O IA  192.168.18.0/24 [110/30] via 192.168.23.2, 00:06:26, Ethernet0/0
O IA  192.168.45.0/24 [110/40] via 192.168.23.2, 00:06:26, Ethernet0/0
O IA  192.168.67.0/24 [110/40] via 192.168.23.2, 00:06:26, Ethernet0/0
O IA  192.168.89.0/24 [110/40] via 192.168.23.2, 00:06:26, Ethernet0/0
O IA  192.168.110.0/24 [110/30] via 192.168.23.2, 00:06:26, Ethernet0/0
O IA  192.168.111.0/24 [110/40] via 192.168.23.2, 00:06:26, Ethernet0/0
O IA  192.168.112.0/24 [110/30] via 192.168.23.2, 00:06:26, Ethernet0/0
R3#

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Author

Commented:
Probably it is supposed to be that way ?  ABR for Stub Area can show the External Routes but other routers in the Stub Area will show  the IA default route instead of External routes
Distinguished Expert 2018
Commented:
It supposed to be like that. ABR has knowledge about all routes from all areas where it connected to (that is characteristic of link state routing protocols), that's why you see external routes - ABR has learned external routes from neighboring routers, but... ABR is filtering LSA type 4 and 5, so stub intra-area routers (above R3) is not getting external routes.

Author

Commented:
Thank you
Distinguished Expert 2018

Commented:
You're welcome.

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