From: Brian McGahan (brian@cyscoexpert.com)
Date: Sat Jul 05 2003 - 18:23:08 GMT-3
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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