From: Erick B. (erickbe@xxxxxxxxx)
Date: Mon Nov 26 2001 - 15:22:28 GMT-3
Hi,
I'm a bit confused on this one. The discussion
regarding the 0/0 makes sense but I just set up a iBGP
connection between 2 routers serial interfaces with no
problems.
R1 --- 192.168.1.x ---- R2
AS100 on both routers.
Loopback on R1 announced in BGP. R2 shows BGP route to
loopback on R1. No other routing protocols and just
directly connected interfaces.
Does this problem show up with a third router in the
mix?
--- John Neiberger <neiby@excite.com> wrote:
> Thanks for that link, it explains the reasoning
> behind the behavior. I
> wanted to note that in my configuration I was not
> using ebgp-multihop since
> these were iBGP peers.
>
> The rationale appears to be the same in both cases:
> a 0/0 route will not
> suffice if that is the only route available to reach
> a BGP peer.
>
> Regards,
> John
>
> On Mon, 26 Nov 2001 10:00:52 +0100, Rivron Francois
> wrote:
>
> | FYI :
> |
> |
>
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/ip_r
> | /iprprt2/1rdbgp.htm#xtocid142341
> |
> | To prevent the creation of loops through
> oscillating routes, the multihop
> | will not be established
> | if the only route to the multihop peer is the
> default route (0.0.0.0).
> | From :
> |
> |
> |
> | > -----Message d'origine-----
> | > De: John Neiberger [SMTP:neiby@excite.com]
> | > Date: lundi 26 novembre 2001 05:33
> | > @: Matt Smith; ccielab@groupstudy.com
> | > Objet: Re: Interesting BGP problem
> | >
> | > I just set this up and was able to verify it in
> 12.1(11). Without at
> | > least
> | > a specific classfull route in the routing table
> the neighbors would
> never
> | > get past ACTIVE. Here is the output from debug
> ip bgp:
> | >
> | > 09:24:03: BGP: 172.16.1.1 multihop open delayed
> 10064ms (no route)
> | > 09:24:13: BGP: 172.16.1.1 multihop open delayed
> 13920ms (no route)
> | > 09:24:14: BGP: Import timer expired. Walking
> from 1 to 1
> | > 09:24:27: BGP: 172.16.1.1 multihop open delayed
> 14560ms (no route)
> | > 09:24:29: BGP: Import timer expired. Walking
> from 1 to 1
> | > 09:24:35: BGP: compute bestpath
> | > 09:24:41: BGP: 172.16.1.1 multihop open delayed
> 14720ms (no route)
> | > 09:24:44: BGP: Import timer expired. Walking
> from 1 to 1
> | > 09:24:56: BGP: 172.16.1.1 multihop open delayed
> 10144ms (no route)
> | >
> | > On this router I then added a static route to
> 172.16.0.0 and the
> neighbors
> | > came up. Very interesting! This definitely
> falls into the "Good to
> Know"
> | > category.
> | >
> | > Thanks,
> | > John
> | >
> | > On Sun, 25 Nov 2001 20:02:24 -0500, Matt Smith
> wrote:
> | >
> | > | Hey all,
> | > | I just got done doing some last minute BGP
> practice scenarios in
> | > preperation
> | > | for my upcoming date with fate on 11/30. At
> any rate I was making
> some
> | > quick
> | > | and dirty lab scenarios to test some varios
> configurations and I
> found
> | > the
> | > | following
> | > |
> | > | R1 <----->R2<------->R3
> | > |
> | > | R1 is configured with a 0.0.0.0 route to R2
> and R3 with a 0.0.0.0
> route
> | > to R2
> | > | as well. I pinged from R1 to R3 and
> communicationed worked fine.
> | > |
> | > | Now I issued router bgp 100 on both R1 and
> R2 and defined the neigh
> bor
> | > | statements for iBGP.
> | > |
> | > | The BGP relationship never came up. AS#s
> were correct on both
> router
> | > | processes and neighbor statements and the IP
> addresses were correct
> as
> | > well.
> | > |
> | > | show ip bgp neighbor reports that neither
> router has sent or
> recieved
> | > and
> | > BGP
> | > | messages and a deb ip packet verifies that
> this is true.
> | > |
> | > | What was the culprit? well........... Make
> a guess then read on
> | > |
> | > |
> | > |
> | > |
> | > |
> | > |
> | > |
> | > |
> | > |
> | > |
> | > |
> | > |
> | > |
> | > |
> | > |
> | > |
> | > |
> | > |
> | > |
> | > |
> | > |
> | > | I issued a static route for the specific
> address of the neighbor on
> | > each
> | > | router (R1 and R3) pointing to R2 and the
> relationship came up.
> | > Apparently
> | > | BGP requires a route in the routing table
> for the nieghbor address
> and
> | > will
> | > | not use the 0.0.0.0 route. IP classless
> enabled on both routers and
> as
> | > I
> | > | stated both routers could ping one another.
> Has anyone ever read
> and
> | > | documentation supporting this to be true? I
> have never seen any
> rules
> | > | pertaining to this issue so I thouht I would
> share it with the
> group.
> | > Just a
> | > | quick tidbit. Hope it helps someone
> someday.
> | > |
> | > | Luck to All
> | > |
> | > | Matt Smith
> | >
>
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