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OSPF Type 5 summarisation at ABR

Unanswered Question
May 7th, 2007
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Is there a way to summarize E1 or E2 routes at a ABR? I cannot summarise this routes at the ASBR because the ASBR's are Dialin and VPN Endpoints which use the same B-Class Subnets therefor I would like to summarize this Network when it goes over to area 0. Area Range and Area Filterlist don't work for me because this commands only influenze Type 1-3 propagtion, and summary adresse can only be implemented on the ASBR, which is not possible because the DIAL-Users get RADIUS assigned IP's. I'm using Cat6K's with Sup720, IOS 12.2(18) SXE4.

Thanks for helping


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limtohsoon Mon, 05/07/2007 - 02:29
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Hi Simon,

If I'm not wrong, you can apply the "summary-address" command at the ABR. It should work. I read about it in one of the books.

Thank you.


Lim TS

vijayasankar Mon, 05/07/2007 - 02:38
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Hi Simon,

I agree that dial-in users will get a dynamic ip from the RADIUS. But wouldn't that be from a deterministic IP address pool?

Usually it will be based on the NAS, a pool will be allocated in RADIUS server.

If your case is different do let me know in details.

If the allocated IP addresses are from a deterministic pool. Then you can have static route to that summary address pointing to null0 with higher metric on the ASBR.

Add the summary address statement under OSPF.

This should help.

This depends how the dyanamic IP Address allocation schema is designed in your network.


nedian123 Mon, 05/07/2007 - 04:02
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Hi Simon,

I think you should make ABR an ASBR by adding a static route say w/ next-hop towards your VPN end point router & redistribute that static route into OSPF which will make ABR an ASBR, now you can easily use summary-address command to summarize class-B prefixes.

Correct me if i misunderstood your problem.

Note: Please don't forget to rate if this was helpful.



simonstoll Mon, 05/07/2007 - 06:47
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Thanks for all your replys, ok, some more details: I have a local pool on each RAS/VPN Device with the address on the first, on the second and so on. All these devices function as ASBR as they redistribute thouse routes in OSPF area 16. There are also some other 10.31.x.x/24 subnets in this area. What I want ist to summarize this Network with on the ABR to area 0. As thouse networks are learned via redistributen, they are Type 5 LSA. Unfortunately I can insert this networks with a "network" statement, that doesn't work on my RAS/VPN devices (AS5350 and VPN3030).

Best regards


nedian123 Tue, 05/08/2007 - 04:29
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Dear Simon,

Add static route on the ABR for these other subnets(10.31.x.x/24) as you mentioned, with next hop pointing to the device from where these subnets are coming. In the second step redistribute these static routes into OSPF making this ABR an ASBR. After doing this you can apply summary-address command to summarize these other subnets....

check this doc it would help you on this:


Note: If this post has helped you don't forget to rate it.


Akhtar Rasool


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