From: Brian McGahan (brian@xxxxxxxxxxxxxxx)
Date: Sat May 11 2002 - 19:33:56 GMT-3
Curtis,
You don't need interesting traffic (dialer-list) for
dialer-watch to work. The side that is watching will always initiate
the call, which means that the remote side does not need interesting
traffic defined, or for that matter even a dial string. Dialer watch,
however, is more usefully applied to other protocols besides OSPF and
RIP. Both OSPF an RIP have demand circuit functions, and neither IGRP,
EIGRP, nor IS-IS have such a function. Dialer watch and demand circuit
have obvious differences in speed of convergence too. With a demand
circuit in OSPF, adjacency is established, databases are exchanged, and
SPF is calculated. Only after this series of events does the demand
circuit go down. With dialer watch, however, routing protocol traffic
should not be defined as interesting. This means that when the line
comes up due to a lost route, adjacency must first be established before
any traffic forwarding can occur. This is really the only option for
EIGRP and IS-IS, however, IGRP and RIP can use snapshot, and OSPF and
RIP have demand circuits (triggered updates in RIP). The demand circuit
of OSPF and RIP can be used in conjunction with dialer-watch, but it
does not make much sense to do so. Dialer-watch is triggered by the
loss of a specific route in your routing table. Demand circuit is
triggered by a change in topology. Assuming that the route being
watched is part of either your OSPF domain or RIP domain, it would
effectively be performing the same function. Also, for dialer-watch to
perform correctly, the DDR link must *never* go down unless the primary
route comes back up. So to answer your question, you most likely
wouldn't use dialer-watch and demand-circuit together, but there's
always an exception to every rule.
HTH
Brian McGahan
CCIE #8593
brian@cyscoexpert.com
CyscoExpert Corporation
Internetwork Consulting & Training
http://www.cyscoexpert.com
Voice: 847.674.3392
Fax: 847.674.2625
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Curtis Phillips
Sent: Saturday, May 11, 2002 4:25 PM
To: ying chang; steven.j.nelson@bt.com; ccielab@groupstudy.com
Subject: Re: Justification for use of Dialer-watch in OSPF
Ying, Steve,
How about the non-dialer-watch side of the connection?
Curtis
----- Original Message -----
From: "ying chang" <ying_c@hotmail.com>
To: <cphillips@suscom.net>; <steven.j.nelson@bt.com>;
<ccielab@groupstudy.com>
Sent: Saturday, May 11, 2002 4:21 PM
Subject: Re: Justification for use of Dialer-watch in OSPF
> Curtis,
>
> I have to agree with Steve. When I did dialer-watch a week or two ago,
I
> could take dialer-group out and the dialer-watch would work without
any
> problems. What triggers dialer-watch to dial is a watched missing
route,
it
> has nothing to do with the interesting traffic specified in the
> dialer-group. After the line come up, it will check if the primary
line
come
> backup every idle-timeout seconds, the line would stay up as long as
the
> route is missing.
>
> Chang
>
>
> >From: "Curtis Phillips" <cphillips@suscom.net>
> >Reply-To: "Curtis Phillips" <cphillips@suscom.net>
> >To: <steven.j.nelson@bt.com>, <ccielab@groupstudy.com>
> >Subject: Re: Justification for use of Dialer-watch in OSPF
> >Date: Sat, 11 May 2002 15:41:39 -0400
> >
> >Steve,
> >
> >I think you will find that demand-circuit is still required if
dialer-watch
> >is used with OSPF.
> >Set it up and you will see that the OSPF will keep the ISDN up.
> >
> >Curtis
> >----- Original Message -----
> >From: <steven.j.nelson@bt.com>
> >To: <cphillips@suscom.net>; <ccielab@groupstudy.com>
> >Sent: Saturday, May 11, 2002 11:53 AM
> >Subject: RE: Justification for use of Dialer-watch in OSPF
> >
> >
> > > Curtis
> > >
> > > Think you may have answered your own question here except for one
small
> > > point.
> > >
> > > Dialer Watch and OSPF Demand circuit are not and were never meant
to
> >work
> >in
> > > conjunction with each other, they are two separate technologies
that
> >allow
> > > demand (Dialer, X.25, atm and frame svc etc etc) circuits to keep
quiet
> > > unless a specific condition is met.
> > >
> > > In the case of ospf demand circuit the trigger is a change in
topology
> >etc
> > > etc
> > >
> > > In the case of Dialer Watch when a watched route dissapears from
the
> >routing
> > > table
> > >
> > > Don't confuse the two and use them as they are meant separately...
> > >
> > > HTH, ant more questions mail me off line...
> > >
> > > All the best
> > >
> > > Steve
> > >
> > > -----Original Message-----
> > > From: Curtis Phillips [mailto:cphillips@suscom.net]
> > > Sent: 11 May 2002 16:29
> > > To: ccielab
> > > Subject: Justification for use of Dialer-watch in OSPF
> > >
> > >
> > > Hello All,
> > >
> > > I was thinking about the use of Dialer-watch with OSPF over ISDN.
I
know
> > > that
> > > demand-circuits are used in conjunction with dialer-watch in the
same
> >manner
> > > as protocol packets are filtered by dialer-lists fro EIGRP or
IGRP.
> > >
> > > Demand interfaces allow the dialer to bypass keep-alives and to
dial
> >only
> > > when there is a change (addition or deletion) of LSA in the OSPF
> >database.
> > >
> > > It seems to me that demand circuits would adequately cover the
> >suppression
> > > of
> > > dial related to anything other than a change in database LSAs. So,
I
> >wonder
> > > what the perceived benefit is of using dialer-watch with OSPF.
Unless
it
> >is
> > > to
> > > track routes that are not in the OSPF process.
> > >
> > > Any thoughts?
> > >
> > > Thanks,
> > >
> > > Curtis
This archive was generated by hypermail 2.1.4 : Thu Jun 13 2002 - 10:58:54 GMT-3