Rod et al,
I now recall the application that required setting the Null route admin
distance to something less than the iBGP distance. Note that iBGP NLRI
comes with other attributes, such as communities. If one is doing filtering
based on communities, then an iBGP path with a filtered community would not
be announced by a router, even though there is a network statement and a
null route. Some applications may require one to filter routes injected by
rtr1, however there may be some exceptions, especially if rtr1 has a path to
a network that rtr2 has, but rtr2 is filtering.
In short, whenever you want to use a locally originated route over any iBGP
learned route, you need to set the admin distance of the null route to less
than the admin distance of iBGP route.
HTH,
chris
> -----Original Message-----
> From: Rod Oliver [mailto:roliver@chello.com]
> Sent: Saturday, July 22, 2000 10:03 AM
> To: cisco-nsp@puck.nether.net
> Subject: RE: [nsp] Question about BGP routing damping
>
>
> I have never had a problem keeping a route in the FIB using a
> static to
> null0 with an admin distance of 250. I think there might be
> an issue if the
> distance is 255, unreachable.
>
> Rod
>
> > -----Original Message-----
> > From: Martin, Christian [mailto:CMartin@mercury.balink.com]
> > Sent: Friday, 21 July 2000 10:35 p.m.
> > To: 'Tatsuya Kawasaki'; cisco-nsp@iagnet.net
> > Subject: RE: [nsp] Question about BGP routing damping
> >
> >
> > The announcing router must have an exact match entry in the
> local FIB in
> > order to announce the route. The one exception is when creating
> > aggregates,
> > in which case, only a prefix-match must be made. If an
> > 'internal' or local
> > path is not available, the prefix will be withdrawn, thus causing
> > route-flapping. Most get around this by routing their static
> > announcements
> > to null0 with a high distance. Some applications require
> you to set this
> > distance to something less than 200, some not.
> >
> > chris
> >
> > > -----Original Message-----
> > > From: Tatsuya Kawasaki [mailto:tatsuya@kivex.com]
> > > Sent: Friday, July 21, 2000 2:56 PM
> > > To: cisco-nsp@iagnet.net
> > > Subject: [nsp] Question about BGP routing damping
> > >
> > >
> > >
> > > Hello,
> > >
> > > I have a simple bgp question.
> > >
> > > In the BGP statement, we defined the network.
> > >
> > > I thought network statement in the bgp statement is
> > > independent of internal routing protocol.
> > > Even if we lost the connectivity to a network,
> > > which does not cause BGP routing damping or does it?
> > >
> > > Only time that BGP routing damping occurs when you lose
> the connection
> > > to peer provided that we do not change any configuration change?
> > >
> > > Or am I missing something?
> > >
> > >
> > > Tatsuya
> > >
> > >
> > > /_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
> > > Tatsuya Kawasaki
> > > Allegiance Telecom
> > > Unlock the Power of the Internet
> > > http://www.kivex.com
> > > Phone 301.215.6777 Fa 301.215.5991
> > > Affiliation given for identification not representation
> > > /_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
> > >
> >
> >
> >
>
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