From: Brian S turner (brian@xxxxxxxxxxxxxxxxx)
Date: Wed Jul 19 2000 - 15:07:10 GMT-3
You cannot make the OSPF hello's uninteresting, because they must establish
the initial adjacency, and from time to time they have to update one another
on link state changes. If the routers are unable to send hellos to
eachother the adjacency will go down. Ip ospf demand suppresses the hellos,
but from time to time they still go. If you filter the hellos the protocol
is broken. Trust me I have tried it and also been told this by some
instructors trying to fix this same problem. The issue was explained
earlier. OSPF demand works fine until you load RIP/EIGRP/IGRP on the router
and assign a Major network, that encompasses the isdn link. Then what
happens is the interface goes down due to idle timer like its supposed to,
because you are suppressing hellos, and have passive interface in your
RIP/IGRP/EIGRP config. But the RIP/IGRP/EIGRP protocol is still being
redistributed into OSPF, so when they see that the ISDN is down, and it is
in the same major network as the one you have turned on for them, they send
out a flash update. Guess who gets the flash update? OSPF!! So, what has
now happened to OSPF? It has a linkstate change. According to the RFC it
has to update its neighbor of the linkstate change, so it brings the ISDN
link back up to pass on the info. Once the update is complete, the hellos
are still suppressed, so after your idle timer, the link goes down again,
and the cycle starts all over again.
Brian Turner
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Jeff Sapiro
Sent: Wednesday, July 19, 2000 10:15 AM
Cc: ccielab@groupstudy.com
Subject: Re: How to configure OSPF over ISDN/DDR
Another item I don't have the equipment to test - I never thought of
making OSPF uninteresting. How can this work? Doesn't there need to be
an initial exchange? It would certainly be an easy generic solution to
all those redistribution scenarios.
-Jeff
Brian Edwards wrote:
> Last time I answered this question I caused a huge raucus. So I'll try
> to be more politically correct this time.There may be some problems
> with OSPF demand circuit is some versions of IOS. The doc states that
> you should only have to configure demand circuit on one side of the
> connection. If this does not work for you try configuring it on both
> sides. If it still doesn't work make OSPF uninteresting in your
> dialer-list. After that upgrade to 12.0 and try all these steps again
> (1 side, both sides, OSPF uninteresting).In the CCIE lab you may not
> have the option of upgrading to 12.0, or you might not want to take
> the time. In this case, IMHO, make OSPF uninteresting (verifiy with
> the proctor if this is acceptable)./Brian
>
> -----Original Message-----
> From: Andy Singh [mailto:ansingh@cisco.com]
> Sent: Tuesday, July 18, 2000 9:31 AM
> To: ccielab@groupstudy.com
> Subject: How to configure OSPF over ISDN/DDR
>
> Hello Can any1 tell me how to configure OSPF over ISDN line
> so hello packets won't bring up the circuit. i think you can
> do "ip ospf demand circuit" inteface command but i can't get
> it to work like that. i'd appreciate any helpAndy
>
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