From: Héctor Fernández (gnakh@telefonica.net)
Date: Wed Aug 24 2005 - 18:43:47 GMT-3
Hi all,
I wouldn't assume you have to make routers neighbor via the ISDN link until
the R6-R7 route is lost.
You're not requested the routers to behave 100% as on-demand circuit. You're
asked the OSPF hello not to dial. You don't need to have the neighbor
relationship up on the ISDN link
What I've done is avoiding ospf from dialing on the dialer list and the
configure the dialer watch.
It has worked ok! Except that when I had dialer map it still told me I had
no dialer map configured... I've changed to dialer string and the moment the
router has been lost, the bri has dialed...
I think we should try to keep configs as simple as possible.
Hictor
----- Original Message -----
From: "Gustavo Novais" <gustavo.novais@novabase.pt>
To: <ccielab@groupstudy.com>
Sent: Wednesday, August 24, 2005 10:25 PM
Subject: Dialer backup without demand circuit
> Hello group
>
> I'm doing an exercise where I have a setup speaking OSPF
>
>
> R2---FR---R4
> | |
> ISDN FR
> | |
> R5---FR---R6
> |
> R7
>
> I'm told the following:
>
> Configure ISDN link between R2 and R5 in the same area. Configure these
> routers such that OSPF hello messages do NOT bring up the link, do NOT
> use ip ospf demand circuit to accomplish this task.
>
> Configure R5 such that if FR link to R6 and/or the ethernet link to R7
> goes down it will automatically bring up ISDN and have full conectivity
> to all networks
>
>
>
>
> My guess initially was to deny ospf packets on dialer-list of R2 and R5,
> to the first part. I tried ip ospf flood reduction to see if I could
> maintin neighborship up as with demand circuit, but tests showed that ip
> ospf flood reduction didn't suppress hellos as on demand-circuit does,
> so neighborship R5-R2 went down, but that would be fine according to the
> question.
>
> I'm left to two options for the second part.
>
> ONE - I thought about dialer-watching routes from R6 and R7. The
> problem is that dialer watch does a AND (all watched routes must be
> down) and I need a OR of the routes. (LOGIC OR one, other or both)
> So, no dialer-watch here.
>
> TWO - backup interfaces - I can configure BRI as backup of both Serial
> to R6 and ethernet to R7. That would work, IF I still allowed OSPF
> hellos to be interesting traffic crossing the ISDN. The backup interface
> is activated when Serial OR Ethernet go down. The problem is that I do
> not have interesting traffic to trigger ISDN link and maintain it up, so
> I'm dead...
>
>
> Am I missing something? Is the exercise impossible? Perhaps if I define
> some kind of RTR probe that matches interesting traffic when ethernet or
> serial are down...
>
>
> Any help is welcome...
>
> Thanks
>
> Gustavo
>
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