From: Michael Schwarz (flying_eskimo@hotmail.com)
Date: Tue Nov 11 2003 - 16:47:24 GMT-3
HDLC was designed for links that used the same subnet for both ends of the
link. PPP was designed so that it could be used in situations where both
sides of the link were on completely different networks, therefore during
the actual negotiation of the PPP protocol, PPP will install a host route to
the remote device. If using the same subnet for both sides of the link you
can of course safely turn this feature off.
Kind of like using HDLC with ip unnumbered on both sides. I think its the
same general idea. Maybe a search on ppp negotiation will provide more
useful results.
Has anyone tried using ip unnumbered on ISDN link (with ospf), does it
follow the same behavior, keeping up the ISDN link? That would be
interesting to know.
michael
----- Original Message -----
From: "Casey, Paul (6822)" <Paul.Casey@o2.com>
To: <ccielab@groupstudy.com>
Cc: "'ccie2be'" <ccie2be@nyc.rr.com>
Sent: Monday, November 10, 2003 11:45 PM
Subject: RE: peer neighbor route.,
> I didnt think it had anything to do with OSPF but more related to PPP.
> All why the /32 is keeping the line up is well documented on the Cisco
> website...!!
> If the ISDN link was HDLC I dont think the same problem would occur.
>
> Anyone, any other explainations of this command..!!
> What is peer neighbor route really for..!!
>
> Kind regards.
> Paul.
>
>
>
> > -----Original Message-----
> > From: ccie2be [SMTP:ccie2be@nyc.rr.com]
> > Sent: Monday, November 10, 2003 9:08 PM
> > To: Casey, Paul (6822); ccielab@groupstudy.com
> > Subject: Re: peer neighbor route.,
> >
> > When redistribution into OSPF is taking place on one of the routers on
one
> > end of the link and the ip subnet of the link is included under the ospf
> > process, using this command stop the isdn link from flapping.
> >
> > I don't remember all the details but the way I understand it is that
> > without
> > this command, when the isdn link comes up (from interesting traffic for
> > example), ospf will install a new /32 route in the route table. When
the
> > link goes down, ospf removes the route, But when the /32 route is
removed
> > that means there's been a topology change. OSPF, being a routing
> > protocol,
> > must, of course, notify all it's neighbors of the topology change and
send
> > out a new LSA to do this. And, this new LSA has to, of course, reach
the
> > other side of the isdn link so ospf brings up the link. Once the link
is
> > up
> > that /32 route is again installed in the route table only to go away
again
> > after the link goes back down. And, so the cycle repeats.
> >
> > To stop this cycle, the no peer neighbor command prevents the /32 route
> > from
> > being installed in the route table in the first place.
> >
> > I forget the roll that redistribution plays in this scenario, but I know
> > that this is explained very well in the book, Troubleshooting IP Routing
> > Protocols in the section on flapping isdn links (or using the ip ospf
> > demand
> > circuit command).
> >
> >
> > ----- Original Message -----
> > From: "Casey, Paul (6822)" <Paul.Casey@o2.com>
> > To: <ccielab@groupstudy.com>
> > Sent: Monday, November 10, 2003 2:39 PM
> > Subject: peer neighbor route.,
> >
> >
> > > Hello,
> > >
> > > I am been looking this peer neighbor route command used under PPP.
> > > Can someone explain to me what this command is actually for,
> > > Yes, I have read that you can remove the /32 host routes it installs
> > from
> > > the far side of the link,
> > > used for ISDN ..by typing the no form of the command.
> > > but what is the purpose of this command when its turned on.
> > >
> > > ex: Why would I want to use this command in the first place - or more
to
> > the
> > > point what can I not do without it,..? What do I need /32 host routes
> > for.
> > > Anyone got an example.
> > >
> > > Cisco website is vague of this stuff. or maybe its just the links I
can
> > find
> > > are vague.
> > >
> > > Any help appreciated.
> > > Kind regards.
> > >
> > >
> > >
> > >
> > >
> >
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