about ospf adj

[jj-zhou]

Hi netpro:

I have two routers , they have been full state ,and I can find each other by show ip os neighbor ,buI they can't recieve peer's route . the interface s0 is point-to-multi and hello-time is 10s ,routerBs int s0 is point-to-point.

[royalblues]

Can you post the configuration of both the routers

Narayan

[Harold Ritter]

This will not work since the two sides will default to different ospf interface types. Try adding "ip ospf network point-to-multipoint" under the interface on each side.

Hope this helps,

[jj-zhou]

Hi hritter:

do you think that the status full can't ensure router receiving route from peer ? both net-type and hello-time must be same.

thank you

[jj-zhou]

Hi hritter:

I have other question, I think that if the two routers have been full ,they had to exchange the ospf DBD inform, so now they can't receive DBD how to form adj ?

thank you

[Harold Ritter · Accepted solution]

Even if you suceed to form a full adjacency by changing the timers to match, the fact that the two routers see the link to each other as a different type will certainly cause ospf to detect an anomaly and not come up with the right topology.

Hope this helps,

[Harold Ritter]

Just to add to my previous comment. If you run a "deb ip ospf spf" in such a scenario, you will see that the LSA is received from the neighbor but that ospf will report the following message when detecting that the link-type is different on either side:

00:11:17: OSPF: Schedule SPF in area 0

Change in LS ID 3.3.3.3, LSA type R, , spf-type Full

00:11:21: OSPF: running SPF for area 0, SPF-type Full

00:11:21: OSPF: Initializing to run spf

00:11:21: OSPF - spf_intra() - rebuilding the tree

00:11:21: It is a router LSA 3.3.3.3. Link Count 3

00:11:21: Processing link 0, id 1.1.1.1, link data 192.168.123.3, type 1

00:11:21: No RTR Back link <++++++ This prevents ospf from considering the link in its topology

As you can see, this router considers the link to the neighbor as a type 1 (point-to-point), where as the other side is seen as a type 2 (transit network).

Hope this helps,

[Harold Ritter]

BTW: Here are the "deb ip ospf spf" output messages from the other router:

00:57:33: OSPF: Initializing to run spf

00:57:33: OSPF - spf_intra() - rebuilding the tree

00:57:33: It is a router LSA 1.1.1.1. Link Count 2

00:57:33: Processing link 0, id 192.168.123.3, link data 192.168.123.1, type 2

00:57:33: Can not find next node 192.168.123.3 listed in LSA LSA type 1, LS ID 1.1.1.1

See how this other router considers the link as a type 2 (transit network).

Hope this helps,

[jj-zhou]

Hi hritter

Your answer is very helpful, the router recevied lsa but it can't use them for spf arithmetic, right ?

[Harold Ritter]

That is correct.

Hope thius helps,