From: Chuck Larrieu (chuck@xxxxxxxxxxxxx)
Date: Sat May 05 2001 - 11:57:27 GMT-3
Hhhmmmm.... You know, that might just explain a phenomenon I have been
seeing.
I've done this a couple of times now - hooked up with people and run BGP
across the internet. ( yes it can be done and yes it offers a lot of
opportunity to try things that would be difficult to duplicate in a modest
home lab. )
Essentially, my compatriot and I will set up BGP between our public side
interfaces. With both iBGP and eBGP, one must use the ebgp-multihop command
On my routers I have my usual default 0.0.0.0 0.0.0.0 ip of my isp router
Things do not come up, and my partner and I fumble around until we try a
defined static - his ip address to next hop my isp router
Doh!
To put this into the study / mastery perspective, it does make sense. BGP
looks for a specific route, not just any old route. It's been a while since
I looked at the RFC, but my recollection is that the RFC assumes directly
connected networks. Multihop and use of loopbacks must be the result of
revisions based on real world experience after the RFC was published.
Chuck
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Norma Schutt
Sent: Friday, May 04, 2001 10:49 PM
To: mcaplan.cs@clearstream.com; ccielab@groupstudy.com
Subject: Re: Default route not good enough for EBGP session
I read somewhere but can't remember where it was now that you can't use a
default route to set up your EBGP sessions. If you aren't using the
directly connected interfaces, then you must have a specific route to the
EBGP neighbor's loopback.
3 days and 7 hours.......
Norma Schutt
At 10:55 AM 5/4/2001, 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
>
>
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