From: Guy Farber (gfarber@xxxxxxxxx)
Date: Sat Jun 02 2001 - 13:10:43 GMT-3
btw I forgot to state the obvious - it suppresses hellos too...
-----Original Message-----
From: Bob Chahal [mailto:bob.chahal@ntlworld.com]
Sent: Sat, June 02, 2001 5:08 PM
To: Guy Farber; ccielab@groupstudy.com
Subject: Re: ISDN/OSPF Demand Circuit
Actually your dead right there. Why use backup interface at all. I don't
know, I wouldn't. It's just a solution from the Bootcamp Lab19 and I've seen
it as a solution in other labs as well.
The solutions may be wrong, they may be correct, but they do make you think
which is good.
Thanks
Bob
----- Original Message -----
From: "Guy Farber" <gfarber@cisco.com>
To: "Bob Chahal" <bob.chahal@ntlworld.com>; <ccielab@groupstudy.com>
Sent: Saturday, June 02, 2001 4:57 PM
Subject: RE: ISDN/OSPF Demand Circuit
> Hi Bob,
>
> When you use isdn to backup a serial line running ospf, obviously want the
> isdn up when the serial is down. Ospf has to refresh LSAs every 30 minutes
> or they age out (by default) of the database. What demand-circuit does for
> you is automatically sets them no to age. It brings up the isdn circuit
only
> when it has an LSA change.
>
> What I don't understand is why use backup interface here...
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Bob Chahal
> Sent: Sat, June 02, 2001 4:50 PM
> To: ccielab@groupstudy.com
> Subject: ISDN/OSPF Demand Circuit
>
>
> I just want to get this clear.
>
> If you configure an ospf isdn demand circuit as a backup to a serial
> interface, the LSA do not age so that's not problem. But why configure
ISDN
> as a demand circuit? Why not just configure it as part of the OSPF domain
> and when the interface goes down the circuit will just come and form an
> adjacency with the other end and synchronise it's ospf database etc etc.
>
> Some practice lab solutions configure the ISDN with ip ospf network
> demand-circuit and then configure backup int bri0 under the serial
> interface. All interfaces on the isdn routers are configured as part of
the
> ospf domain but I think this works fine without the demand-circuit config.
> Interesting traffic permits all ip and the only other thing is that only
one
> end of the isdn circuit actually initiates the call.
>
> I think I'll lab all this out again but I'd be interested to hear what
> people might think.
>
> Thanks
>
> Bob
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