From: Brian McGahan (brian@cyscoexpert.com)
Date: Wed Jul 09 2003 - 14:06:46 GMT-3
Jim,
Both sides of the connection should be able to dial. Therefore
no matter where the topology change occurs, either side can bring up the
link to report this change.
It doesn't matter which side you configure the command 'ip ospf
demand-circuit' on. For clarity, I usually put it on both sides so you
can see it in the config. It's only necessary on one side though.
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: Monday, July 07, 2003 6:20 PM
> To: Group Study; Brian McGahan
> Subject: Re: OSPF Demand Circuit
>
> 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
> > > > >
> > > > >
> > > > >
> > > >
> >
This archive was generated by hypermail 2.1.4 : Wed Aug 06 2003 - 06:52:30 GMT-3