OSPF conflict

Answered Question
Aug 11th, 2008

I introduced a new ospf area number into our network, and it seemed to cause routing problems. Internally everything was reachable, but when I vpn'd in to our network I could not telnet into some or our routers, it also seemed to take down 2 of the servers public access which are NATed from public to private. With a show ip route the ASA showed the new area as getting the route through OSPF IA (inter area). When the new area was introduced I put the hello-interval as 1 and the dead interval as 5, where as the other OSPF intervals are default. When I shutdown the router that housed the new OSPF area, all services came back up. Would the intervals have caused this problem? Any help is appreciated. Thanks

I have this problem too.
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Correct Answer by Richard Burts about 8 years 4 months ago

Cole

Thanks for the diagram. While it is helpful I do not think that it shows us enough to understand this issue. If the OSPF timers were set differently I would expect that it would not have formed neighbor relationships with any router with default timers. But I get the feeling that if it were on the 3750 at the end of the line that it might not have had neighbors on that area anyway. Is that correct?

Perhaps you can tell us a bit more about what was previously configured for OSPF and what you did when you added the new area. What was the area ID of the existing area? What was the area ID of the new area? Was the existing area a normal area, stub area, or anything special? Was the new area a normal area, stub area, or anything special?

The symptoms sound almost like the new area generated a different default route or over rode some existing routes. Is this possible?

HTH

Rick

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colegisselbeck Mon, 08/11/2008 - 20:18

Also, when we were experiencing this, the public internet from our LAN was unreachable. Thanks

royalblues Mon, 08/11/2008 - 22:13

Need more info on your topology

can you post a brief network diagram which shows the introduction of the new area as well

Narayan

Correct Answer
Richard Burts Tue, 08/12/2008 - 04:39

Cole

Thanks for the diagram. While it is helpful I do not think that it shows us enough to understand this issue. If the OSPF timers were set differently I would expect that it would not have formed neighbor relationships with any router with default timers. But I get the feeling that if it were on the 3750 at the end of the line that it might not have had neighbors on that area anyway. Is that correct?

Perhaps you can tell us a bit more about what was previously configured for OSPF and what you did when you added the new area. What was the area ID of the existing area? What was the area ID of the new area? Was the existing area a normal area, stub area, or anything special? Was the new area a normal area, stub area, or anything special?

The symptoms sound almost like the new area generated a different default route or over rode some existing routes. Is this possible?

HTH

Rick

colegisselbeck Tue, 08/12/2008 - 08:18

Got my issue resolved when I looked at the config more closely noticed that there was default-information originate always in it. So it was propagating it's default route to the rest of our routers in the network. Thanks for your guys' help.

Cole

Richard Burts Tue, 08/12/2008 - 08:21

Cole

Thanks for posting back to the thread and indicating that you had found the problem and solved it. It looks like my guess that it was an issue with default route from the new area was correct. Thanks for using the rating system to indicate that your problem was resolved (and thanks for the rating). It makes the forum more useful when people can read about a problem and can know that there were responses which did lead to a solution for the problem.

The forum is an excellent place to learn about Cisco networking. I encourage you to continue your participation in the forum.

HTH

Rick

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