From: Jay Hennigan (jay@xxxxxxxx)
Date: Mon Oct 15 2001 - 13:46:38 GMT-3
On Mon, 15 Oct 2001, Thomas Larus wrote:
> I know there has been a lot of discussion of this problem, as apparently ther
e
> is a bootcamp lab dealing with it, but I don't remember seeing an answer yet
> that would work in my lab situation.
>
> I have an isdn link acting as an alternative path to a FR link. ISDN and FR
> links go between the same two routers. The FR link is in area 0, and the isd
n
> link is in area 1. I have tried having both in area 0 and have the isdn
> link's area be a NSSA area. Still the 224.0.0.5 OSPF LSA multicast keeps
> bring the isdn link up right after it went down. And the thing that brings it
> up seems to be the very change in the OSPF link state database brought about
> by the ISDN link going down.
Are you redistributing OSPF to another routing protocol anywhere? That's
the most common reason for this. The solution is to filter the route of
the ISDN link itself from the redistribution.
> I have DLSW going over this backbone, but that is not bringing up the link.
> Both sides of the link are in the same BGP AS, so there's no BGP issue here.
> I have tried getting ip ospf demand-circuit to work before in a much simpler
> config, and no luck.
Can you get it to work in a pure OSPF environment? Are your bandwidths and
costs such that the frame link is preferred, and the routers aren't trying
to do equal-cost load balancing?
> I only have native isdn support on one side of the isdn link (I use an Adtran
> TA on the other side), but sh ip ospf int shows that ip ospf demand-circuit i
s
> working on both routers and that hellos are being suppressed, so the
> non-native isdn router situation does not seem to be an issue.
You should only *configure* it on one side, but you should see the hellos
suppressed on both. I'm not sure if the TA situation would be a factor.
It shouldn't, because you can do aux-to-aux OSPF demand circuits.
-- Jay Hennigan - CCIE #7880 - Network Administration - jay@west.net NetLojix Communications, Inc. - http://www.netlojix.com/ WestNet: Connecting you to the planet. 805 884-6323
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