confusing EIGRP behaviour

Answered Question
Feb 21st, 2007

hello,

we have two site connected over MPLS (PRI) and ISDN (BACKUP). today the MPLS connection went down and accordingly ISDN dialed and connected but something strange happened, on the remote site as well as HO site it was showing connected and i could even telnet from HO to remote site on the dialer ip address, still i could not ping the local interfaces of both each or any other machine inside the networks from one another.

When i check the ip route i found that EIGRP didn't changed routes and thus both routers although were connected through ISDN but still no exchange of routes were happening.

the remote router has identical configuration as the other remote router has and the other one works prefectly if the PRI link fails.

any one has any idea what it could be? any help would be really helpful

I have this problem too.
0 votes
Correct Answer by Richard Burts about 9 years 7 months ago

Zulqurnain

I have looked at the config that you posted and I see several problems in it.

- the dialer map does not include the broadcast keyword. Without specifying broadcast then the multicast EIGRP packets will not be transmitted over the ISDN backup.

- the EIGRP network statement and mask:

network 3.3.0.0 0.0.0.255

mean that it is looking for 3.3.0 but the ISDN interface address is 3.3.3 so EIGRP will not process on the ISDN interface.

HTH

Rick

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Overall Rating: 4.5 (2 ratings)
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spremkumar Wed, 02/21/2007 - 23:23

Hi

Can you post the config of the router and also the output of show isdn active/show isdn status/show ip route taken out from both the routers ?

Also did you check the status of primary interfaces when the isdn is connected ?

Sometimes when your are checking your physical loop on the primary line its shows up/up and may affect traffic/routing change to the secondary route/interface..

regds

zulqurnain Wed, 02/21/2007 - 23:49

hello,

check the remote branch config attached

the primary link was already down and just to confirm it more i shutdown the pri interface also.

still it was the same..

Correct Answer
Richard Burts Thu, 02/22/2007 - 09:57

Zulqurnain

I have looked at the config that you posted and I see several problems in it.

- the dialer map does not include the broadcast keyword. Without specifying broadcast then the multicast EIGRP packets will not be transmitted over the ISDN backup.

- the EIGRP network statement and mask:

network 3.3.0.0 0.0.0.255

mean that it is looking for 3.3.0 but the ISDN interface address is 3.3.3 so EIGRP will not process on the ISDN interface.

HTH

Rick

zulqurnain Sat, 02/24/2007 - 01:25

hello,

thanks alot it worked. i can't believe i made a silly mistake and i couldn't notice it even though i must have cross checked the config with other routers million times.. once again thanks alot.

Richard Burts Sat, 02/24/2007 - 19:31

Zulqurnain

Thanks for using the rating system to indicate that your problem was solved (and thanks for the rating). It makes the forum more usable when people can read about a problem and can know that they will be able to read a solution to the problem.

I encourage you to continue your participation in the forum.

HTH

Rick

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