From: ccie2be (ccie2be@nyc.rr.com)
Date: Mon Jul 07 2003 - 20:20:17 GMT-3
Hi Brian,
This is too funny. At first, I had no idea what you were talking about
until I realized you answered the question I had asked rather then the
question I had meant to ask. And, as it turns out I'm glad I wasn't clear
because your answer brings up another issue I've been trying to figure out.
I'm under the impression that when using the ip ospf demand circuit command,
it doesn't matter which side dials out. In other words, the side of the
link which has ip ospf demand-circuit configured can either be side that
makes the call or the side that receives the call. Is this true?
Also, when using the ip ospf demand-circuit feature, should both sides of
the link be able to place calls so that no matter where a topology change
occurs, the change can be announced over the isdn link ?
Now, in the hub and spoke situation you describe, is there a "best practice"
as far as on which router to configure the ip ospf demand circuit and which
routers should place the calls?
I've been taught that it's better to have spoke routers dial into the hub
router because it's "cleaner". But, it seems to to me that the hub router
has to be able to dial out to the spokes because otherwise how could the hub
router announce a change it heard from one spoke to the other spokes.
I'm sorry for all the questions; I really hope I'm not being too much of a
pest. At first, using the ip ospf demand circuit doesn't seem like a big
deal, but then when I try getting it work properly I discover how much I
don't know. Ughg!!!
Thanks so much. Jim
----- Original Message -----
From: "Brian McGahan" <brian@cyscoexpert.com>
To: "'ccie2be'" <ccie2be@nyc.rr.com>; "'Group Study'"
<ccielab@groupstudy.com>
Sent: Saturday, July 05, 2003 5:23 PM
Subject: RE: OSPF Demand Circuit
> Jim,
>
> Your BRI interface is a non-broadcast multipoint interface.
> Therefore, you can have multiple neighbors on a segment if you wanted.
> Suppose you are running ISDN hub and spoke. If there is more than one
> neighbor on the segment, you can't run OSPF as network point to point.
>
> HTH
>
> Brian McGahan, CCIE #8593
> Director of Design and Implementation
> brian@cyscoexpert.com
>
> CyscoExpert Corporation
> Internetwork Consulting & Training
> Toll Free: 866.CyscoXP
> Fax: 847.674.2625
>
>
> > -----Original Message-----
> > From: ccie2be [mailto:ccie2be@nyc.rr.com]
> > Sent: Saturday, July 05, 2003 7:42 AM
> > To: Group Study; Brian McGahan
> > Subject: Re: OSPF Demand Circuit
> >
> > Hi Brian,
> >
> > Thanks for your reply.
> >
> > In another ospf related post, I was wondering about the reason or
> benefit
> > for changing the network type from it's default to point to point.
> Nobody
> > (as yet ) posted a response. Do you know under what circumstances
> this is
> > something that should (or is required) be done? Thanks very much.
> Jim
> >
> > ----- Original Message -----
> > From: "Brian McGahan" <brian@cyscoexpert.com>
> > To: "'ccie2be'" <ccie2be@nyc.rr.com>; "'Group Study'"
> > <ccielab@groupstudy.com>
> > Sent: Friday, July 04, 2003 1:41 PM
> > Subject: RE: OSPF Demand Circuit
> >
> >
> > > Jim,
> > >
> > > This TAC document is wrong. The purpose of running OSPF demand
> > > circuit is to maintain an accurate view of the routing topology,
> while
> > > minimizing the amount of time that your DDR link is up solely due to
> > > routing protocol traffic.
> > >
> > > By denying OSPF as interesting traffic, adjacency cannot be
> > > maintained over the DDR link unless it is up for some other reason.
> > > When the link goes down due to no interesting traffic passing over
> the
> > > link within the idle timeout, OSPF adjacency will be lost as soon as
> the
> > > dead interval expires.
> > >
> > > When running OSPF demand circuit, OSPF *should* be specified as
> > > interesting traffic.
> > >
> > > HTH,
> > >
> > > Brian McGahan, CCIE #8593
> > > Director of Design and Implementation
> > > brian@cyscoexpert.com
> > >
> > > CyscoExpert Corporation
> > > Internetwork Consulting & Training
> > > Toll Free: 866.CyscoXP
> > > Fax: 847.674.2625
> > >
> > >
> > > > -----Original Message-----
> > > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
> Behalf
> > > Of
> > > > ccie2be
> > > > Sent: Friday, July 04, 2003 5:22 AM
> > > > To: Group Study
> > > > Subject: OSPF Demand Circuit
> > > >
> > > > Hi,
> > > >
> > > > After checking the archieves, I didn't find anything that
> specifically
> > > > addressed this question, so here goes.
> > > >
> > > > I thought that when a BRI interface is configured as an ip ospf
> > > > demand-circuit, it will automatically suppress ospf hello's as
> long as
> > > the
> > > > interface is configured as a p2p or p2m ospf network type.
> > > >
> > > > However, in the example at
> > > > http://www.cisco.com/warp/public/129/config-bri-map.html , it
> shows an
> > > > access
> > > > list being used to prevent ospf hello's in addition to the ip ospf
> > > > demand-circuit command being configured.
> > > >
> > > > Is it really necessary (or just sometimes necessary) to use an
> access
> > > list
> > > > to
> > > > deny ospf hello's (packets addressed to 224.0.0.5) when one side
> of
> > > the
> > > > isdn
> > > > circuit is configured as an ip ospf demand circuit? If so, why is
> > > that?
> > > > Also, if the access-list in addtion to the ip ospf demand circuit
> is
> > > only
> > > > needed in certain situations, what are those situations?
> > > >
> > > > Thanks, Jim
> > > >
> > > >
> > > >
> > >
> _______________________________________________________________________
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