From: Johnny Dedon (johnny.dedon@xxxxxxxxxx)
Date: Wed May 09 2001 - 14:44:38 GMT-3
Guys,
Rodgers is correct in his analysis.
The following note is directly off of the CCO DOCS for BGP.
Note To avoid the accidental creation of loops through oscillating routes,
the multihop session will not be established if the only route to the
multihop peer's address is the default route (0.0.0.0).
Johnny Dedon
Senior Staff Consultant
Exodus Professional Services
johnny.dedon@exodus.net
www.exodus.net
----- Original Message -----
From: "Rodgers Moore" <rodgers@the-moores.org>
To: <mcaplan.cs@clearstream.com>
Cc: <ccielab@groupstudy.com>
Sent: Wednesday, May 09, 2001 12:12 PM
Subject: Re: Default route not good enough for EBGP session
> Two problems, you have a routing loop and you didn't define a network to
advertise to the other
> router. The BIG problem is the routing loop. When you change one of the
routes to be specific,
> you fix the problem. What I suspect is, that you need to turn off route
caching, if you want it
> to work with the routing loop in place.
>
> Rodgers Moore
>
> mcaplan.cs@clearstream.com wrote:
>
> > HI,
> >
> > I have a very simple set up
> >
> > (lo 0)R1----frame PVC-----R2(lo 0)
> >
> > Configs ar shown below. I am setting up EBGP between R1 and R2, using Lo
0
> > as the peer IP address in both cases. I can do an extended ping from R1
to
> > R2 usng Lo 0 as the source address. The neighbor relationship however
will
> > not progress beyond active.
> > The following is the output from debug ip bgp
> >
> > 03:59:52: BGP: 11.11.11.11 multihop open delayed 19344ms (no route)
> >
> > There is a route, but it just happens to be the default route. It all
works
> > fine if I put a more precise route onto R1 or R2. Why does it fail with
> > default routes, when extended ping works fine ?
> >
> > R1
> >
> > interface Loopback0
> > ip address 10.10.10.10 255.255.255.255
> > no ip directed-broadcast
> > !
> > interface Serial0
> > ip address 12.1.1.1 255.0.0.0
> > no ip directed-broadcast
> > encapsulation frame-relay
> > !
> > router bgp 1
> > neighbor 11.11.11.11 remote-as 2
> > neighbor 11.11.11.11 ebgp-multihop 255
> > neighbor 11.11.11.11 update-source Loopback0
> > !
> > ip classless
> > ip route 0.0.0.0 0.0.0.0 12.2.2.2
> >
> > Gateway of last resort is 12.2.2.2 to network 0.0.0.0
> >
> > 10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
> > C 10.10.10.10/32 is directly connected, Loopback0
> > C 10.1.0.0/16 is directly connected, TokenRing0
> > C 12.0.0.0/8 is directly connected, Serial0
> > S* 0.0.0.0/0 [1/0] via 12.2.2.2
> >
> > R2
> >
> > interface Loopback0
> > ip address 11.11.11.11 255.255.255.255
> > no ip directed-broadcast
> > !
> > interface Serial0
> > ip address 12.2.2.2 255.0.0.0
> > no ip directed-broadcast
> > encapsulation frame-relay
> > no ip route-cache
> > no ip mroute-cache
> > logging event subif-link-status
> > logging event dlci-status-change
> > no fair-queue
> > clockrate 2000000
> > !
> > router bgp 2
> > neighbor 10.10.10.10 remote-as 1
> > neighbor 10.10.10.10 ebgp-multihop 255
> > neighbor 10.10.10.10 update-source Loopback0
> > !
> > ip classless
> > ip route 0.0.0.0 0.0.0.0 12.1.1.1
> >
> > Gateway of last resort is 12.1.1.1 to network 0.0.0.0
> >
> > 11.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
> > C 11.11.11.11/32 is directly connected, Loopback0
> > C 11.1.0.0/16 is directly connected, Ethernet0
> > C 12.0.0.0/8 is directly connected, Serial0
> > S* 0.0.0.0/0 [1/0] via 12.1.1.1
> >
> > Any advice with this strange behaviour ?
> >
> > Cheers
> >
> > Mark
> >
> > Visit us at http://www.clearstream.com
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