From: steven.j.nelson@xxxxxx
Date: Sun May 12 2002 - 12:52:36 GMT-3
Curtis,
Brians explanation is well presented and correct, but as you have read now
that demand circuit is not needed to run dialer watch to backup a watched
link.
However I never said that it couldn't be used I hust stated that it was not
meant to work that way, i.e that the two are separate, not mutually
exclusive if you will.
I would learn both techniques if I was you, I have seen some commercial
scenarios that ask you to back up a link and they have specifically stated :
"Do not use demand circuit, floating static routes or default routing to
accomplish this" If this was a question on a real lab then your
understanding would be flawed.
Anyway if you need any more pointers or configs, drop me line I should be
able to help out.
Thanks HTH
Steve
-----Original Message-----
From: Curtis Phillips [mailto:cphillips@suscom.net]
Sent: 12 May 2002 01:28
To: Brian McGahan; 'ying chang'; Nelson,SJ,Steven,IVNH25 C; ccielab
Subject: Re: Justification for use of Dialer-watch in OSPF
A better example showing OSPF clearly has to be prevented from bringing up
the link.
http://www.cisco.com/warp/public/129/bri-backup-map-watch.html
----- Original Message -----
From: "Brian McGahan" <brian@cyscoexpert.com>
To: "'Curtis Phillips'" <cphillips@suscom.net>; "'ying chang'"
<ying_c@hotmail.com>; <steven.j.nelson@bt.com>; <ccielab@groupstudy.com>
Sent: Saturday, May 11, 2002 6:33 PM
Subject: RE: Justification for use of Dialer-watch in OSPF
> 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 - 10:58:55 GMT-3