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Summarizing routes with OSPF

Hello,

I am starting to play with OSPF in GNS3 and I cannot get my routes to summarize in the routing tables of R1 and R2. The routing tables are as follows:

R1#sh ip route

Gateway of last resort is not set

     1.0.0.0/32 is subnetted, 1 subnets

C       1.1.1.1 is directly connected, Loopback10

     10.0.0.0/8 is variably subnetted, 10 subnets, 2 masks

O       10.2.10.0/24 [110/20] via 10.0.0.6, 00:18:04, FastEthernet0/1

C       10.1.3.0/24 is directly connected, Loopback3

C       10.1.2.0/24 is directly connected, Loopback2

C       10.1.1.0/24 is directly connected, Loopback1

C       10.0.0.0/30 is directly connected, FastEthernet0/0

C       10.0.0.4/30 is directly connected, FastEthernet0/1

C       10.1.4.0/24 is directly connected, Loopback4

O       10.2.30.0/24 [110/20] via 10.0.0.6, 00:18:05, FastEthernet0/1

O       10.2.20.0/24 [110/20] via 10.0.0.6, 00:18:05, FastEthernet0/1

O       10.2.40.0/24 [110/20] via 10.0.0.6, 00:18:05, FastEthernet0/1

R1#

---------------------------------------------------------------------------------------------------------------

R2#sh ip route

Gateway of last resort is not set

     10.0.0.0/8 is variably subnetted, 10 subnets, 3 masks

C       10.2.10.0/24 is directly connected, FastEthernet0/1.10

O       10.1.2.1/32 [110/11] via 10.0.0.5, 06:05:30, FastEthernet0/0

O       10.1.3.1/32 [110/11] via 10.0.0.5, 06:05:30, FastEthernet0/0

O       10.0.0.0/30 [110/20] via 10.0.0.5, 06:05:30, FastEthernet0/0

O       10.1.1.1/32 [110/11] via 10.0.0.5, 06:05:30, FastEthernet0/0

O       10.1.4.1/32 [110/11] via 10.0.0.5, 06:05:30, FastEthernet0/0

C       10.0.0.4/30 is directly connected, FastEthernet0/0

C       10.2.30.0/24 is directly connected, FastEthernet0/1.30

C       10.2.20.0/24 is directly connected, FastEthernet0/1.20

C       10.2.40.0/24 is directly connected, FastEthernet0/1.40

R2#

I have put in summary addresses in the configs of both routers (attached) but R1's routing table won't summarize the 10.2.x.x networks and R2 won't summarize the 10.1.x.x networks. Am I doing something wrong?

Thanks in advance

Matt

1 ACCEPTED SOLUTION

Accepted Solutions

Hi,

you can't summarize or filter within the same OSPF area because the link-state databases have to be  the same on all routers in an area.

You can summarize OSPF internal routes on ABRs (area border router) between areas and external routes on ASBRs (autonomous system boundary router), where they are injected into OSPF.

HTH

Rolf

View solution in original post

5 REPLIES 5

They are both 3725's running C3725-ADVENTERPRISEK9-M), Version 12.4(15)T14 by the way

Hi,

you can't summarize or filter within the same OSPF area because the link-state databases have to be  the same on all routers in an area.

You can summarize OSPF internal routes on ABRs (area border router) between areas and external routes on ASBRs (autonomous system boundary router), where they are injected into OSPF.

HTH

Rolf

View solution in original post

Thank you good sir!

You're welcome! Thanks for rating and marking as answered!

ashirkar
Rising star

Hello Matthew,

This doc might help you to understand ospf inter-area summarization

https://supportforums.cisco.com/docs/DOC-27672

Regards,

Ashish Shirkar