From: Scott Morris (swm@emanon.com)
Date: Sat Jul 05 2003 - 13:25:56 GMT-3
They are two different concepts though...
The 'broadcast' parameter is used so that OSPF can run period.
Otherwise, there is no concept of multicast/broadcast usage on the link,
up or down.
If you are using 'demand circuit', it will suppress the hellos by
itself, so nothing is really needed for interesting traffic.
If you are not using 'demand circuit', then you need to exclude OSPF
from the interesting traffic so that you link doesn't stay up all the
time. Once the BRI circuit is up (caused be whatever you do deem
interesting, or dialer-watch, or floating static, or whatever), then
everything will run across the line.
Remember, the ACL is only defining what is "interesting", not what is
allowed or not to go across the line.
HTH,
Scott
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
ccie2be
Sent: Saturday, July 05, 2003 8:33 AM
To: Group Study; Brian McGahan
Subject: Re: OSPF Demand Circuit
Hi Brian,
Thanks for gettting back to me.
In another earlier post, someone wrote that the reason for denying ospf
traffic was because in the dialer map included the broadcast keyword
which would keep the circuit up unless the access-list denied ospf
hello's. Did you see that post? This sounded reasonable to me so it's
a very good thing I got your email.
Also, although this is a scary thought, it's good to know that you can't
believe everything you see on the cisco web site. I hope there aren't
too many incorrect examples there.
Happy 4th of July :-)
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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> >
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