From: DAN DORTON (DHSTS68@xxxxxxxxxxxxxxx)
Date: Mon Apr 29 2002 - 17:10:18 GMT-3
I usually work under the idea that if there is a route-reflector
invloved & I cannot turn off sync then look at using confederations.
With a single P2P IBGP link you can get away with injecting the
networks into the IGP, but when route-reflectors come into play more &
more problems can arise (depending on your IGP & it's confguration).
Rick is right in that there is no true solution for the problem he just
presented under the rules applied to it.
(At least if you need to get the routes there via BGP. Otherwise you
could use NAT, policy routing, etc)
I think what peter means is that in a real world situation a
configuration like this would not make any sense.
Although fully meshing a large IBGP scenario might be a bit out of
reach financially for some customers, so you might still need RR's.
In any case in a "real world" situation turning off sync would be
entirely up to you & if you trust you locally routed domain then there
would not be a problem.
The CCIE lab is designed to make damn sure that you know how/why & when
a technology works, or doesn't.
Sometimes in order to test it properly it must be presented in a
ridiculas fashion.
>>> "Bauer, Rick" <BAUERR@toysrus.com> 04/29/02 01:57PM >>>
Here is the topology;
loop0---r1---e0---e0---r2
loop1---
Loop0 200.200.200.1/25
Loop1 200.200.200.129/25
Here are the rules; You can not use static routes, loopback routes can
not
appear in the IGP!, and you can not disable sync.
Now with IBGP will the routes sync on r2? No.
r4#sho ip bgp 200.200.200.0
BGP routing table entry for 200.200.200.0/25, version 0
Paths: (1 available, no best path)
Not advertised to any peer
Local
172.16.13.1 (metric 1323) from 172.16.13.1 (200.200.200.129)
Origin IGP, metric 0, localpref 100, valid, internal, not
synchronized
r4#sho ip bgp 200.200.200.128
BGP routing table entry for 200.200.200.128/25, version 0
Paths: (1 available, no best path)
Not advertised to any peer
Local
172.16.13.1 (metric 1323) from 172.16.13.1 (200.200.200.129)
Origin IGP, metric 0, localpref 100, valid, internal, not
synchronized
The best way to work around this is to use a confederation so that the
as
are external.
Now go drink a beer.
-----Original Message-----
From: Peter van Oene [mailto:pvo@usermail.com]
Sent: Monday, April 29, 2002 2:39 PM
To: Bauer, Rick; 'ccielab@groupstudy.com'
Subject: RE: BGP OSPF sync with Route Reflecter
Why would the routes not be in the IGP if you were using Synch? Synch
is
designed to support IGP based transit for BGP networks. Are you
getting
around this by eliminating the IBGP? This answer seems unrelated to
the
usual question which is how to make synch work with route
reflection. Maybe that wasn't the question in this case and I missed
it. I'm not sure I understand the p2p reference either. I should
likely
get drunk before reading this list as its getting pretty wacky these
days.
Pete
At 02:25 PM 4/29/2002 -0400, Bauer, Rick wrote:
>Except for the fact that synchronization is enabled, the routes are
not in
>IGP, and you can't use statics. Full mesh IBGP won't help because you
need
>EBGP to relieve the sync issue. You can suffer from the same sync
issues on
>a p2p link where there are no sub-optimal routing issues. I am not
>recommending to use this in the real world. What I am suggesting is
that
>people understand how bgp works and how to make it work with certain
>restrictions.
>
>-----Original Message-----
>From: Peter van Oene [mailto:pvo@usermail.com]
>Sent: Monday, April 29, 2002 2:14 PM
>To: Bauer, Rick; 'ccielab@groupstudy.com'
>Subject: RE: BGP OSPF sync with Route Reflecter
>
>
>Well, first off, a routed network where each router is a confederate
sub-as
>would deliver lots of sub-optimal routing. Further, reconfiguring
one's
>network into such a kludge simply to make an antiquated feature work
is
>really not something I'd advise.
>
>I would much rather full mesh my IBGP than confederate in this ugly
case.
>
>Pete
>
>
>At 02:09 PM 4/29/2002 -0400, Bauer, Rick wrote:
> >Why is that?
> >
> >-----Original Message-----
> >From: Peter van Oene [mailto:pvo@usermail.com]
> >Sent: Monday, April 29, 2002 1:29 PM
> >To: ccielab@groupstudy.com
> >Subject: RE: BGP OSPF sync with Route Reflecter
> >
> >
> >if this is the solution, I would suggest that the question is
seriously
> >flawed.
> >
> >At 08:58 AM 4/29/2002 -0400, Bauer, Rick wrote:
> > >Actually, a confederation is the way to work around the sync
issue, if
>you
> > >can not disable sync, or put the routes in the igp, or add statics
to
the
> > >ibgp peer receiving the routes. HTH....
> > >
> > >-----Original Message-----
> > >From: Joe Higgins [mailto:netsat@optonline.net]
> > >Sent: Sunday, April 28, 2002 9:03 AM
> > >To: Michael Jia
> > >Cc: ccielab@groupstudy.com
> > >Subject: Re: BGP OSPF sync with Route Reflecter
> > >
> > >
> > >This scenario of bgp and ospf over a route reflector setup in
absolute
> >terms
> > >cannot work because of the inherent design of ospf and bgp.
Previous
>posts
> > >explain why this is so. I suggest that if one finds oneself in a
>situation
> > >where they find it impossible to put in the "no synchronization"
command
> > >then
> > >they should start thinking outside the "BOX" and possible peer
the
>route
> > >reflector clients with each other, or run igrp or eigrp on top of
ospf
on
> > >the
> > >route reflector portion of their network. This horse has been
beaten up
> > >pretty
> > >badly. Good luck.
> > >Joe H.
> > >
> > >Michael Jia wrote:
> > >
> > > > Hi,
> > > >
> > > > I have a general question regarding BGP and OSPF sync when
router
> > >reflector
> > > > is
> > > > used. I've seen some threads discuss it before on the list.
> > > >
> > > > The scenerio is like :
> > > >
> > > > R1 ---- R2------ R3
> > > >
> > > > All R1, R2, R3 are in same AS, R1 and R3 peer to external AS.
> > > > R2 is the route reflecter with iBGP peered to both R1 and R3.
> > > > R1 and R3 doesn't peer with each other.
> > > > OSPF is used as IGP for R1, R2 and R3.
> > > >
> > > > When a eBGP route is redistritued at R1 into OSPF. The route's
> > > > BGP id is R1, its OSPF id is also R1.
> > > > iBGP syncs at R2 without question.
> > > >
> > > > However, it doesn't sync at R3. Because from R3, it sees iBGP
id as
>R2,
> > > > the Reflector's ID, but OSPF id is still R1. (Am I right?
please
>correct
> > >me
> > > > if my logic is wrong. At a live lab, if R3 peer with R1 , the
route
>will
> > > > sync
> > > > immediatly. In R3's routing table, it clearly has the route and
the
>next
> > >hop
> > > > route as OSPF routes. )
> > > >
> > > > The question is, how to make it sync without using "no sync" at
R3?
> > > >
> > > > Thanks a lot.
> > > >
> > > > Michael
> > > >
This archive was generated by hypermail 2.1.4 : Thu Jun 13 2002 - 10:58:22 GMT-3