OSPF Route Summary

Unanswered Question
May 17th, 2007


I have a range of network addresses that I would like to summarize into area 0.

router ospf 100


network area 70

network area 0

network area 0

I was thinking I could just summarise the address range saying if you want to get to anything come to me. So I used the command

area 70 range

My worry here is I learn a lot of routes to networks such as, I just want to make sure that my core routers won't send traffic into area 70 when a route to exists.

I have this problem too.
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Harold Ritter Thu, 05/17/2007 - 07:22


You need to use the "area 70 range" command when you want to summarize routes from this specific area into area 0. Using "area 0 range" would summarize routes from area 0 rather than to area 0.

Hope this helps,

sundar.palaniappan Thu, 05/17/2007 - 07:04 would suppress more specific routes in this range. Any routes such as would be advertised as it is and wouldn't be summarized as it doesn't fall within the 'area range' scope you configured on the ABR. You should have no problems with your proposed configuration.



sundar.palaniappan Thu, 05/17/2007 - 07:32

Yes, as hritter stated the area id used in the area range command identifies the native area of the route(s) that's being summarized. In this case subnets of exist in area 70 and are being summarized into area 0.


Another thing to bear in mind is if there are multiple ABRs connecting area 70 you need to configure the 'area range' command on all of them otherwise the more specific subnets will be leaked through another ABR.



gavin.mckee Thu, 05/17/2007 - 22:50

Thanks Sundar,

I had been using the area 70 command and tried it again with the area 0 command and found that area 0 does not work, so I just reverted to my orignal configuration.

Thanks for the help.

Note the rating!



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