From: McClure, Allen (Allen.McClure@Yum.com)
Date: Mon Sep 08 2003 - 15:16:29 GMT-3
I could be off here, but have you experimented with using the distance
command to make OSPF routes preferred over eBGP routes in the routing
table? Just a quick thought; sorry if I'm off base. My thought is that
you are trying to transport BGP prefixes between the two AS's, not use
BGP for routing. So, I'd use distance to prefer your IGP.
Let me know how it turns out!
Allen G. McClure
CCNP/CCDP/MCSE
Yum! Brands, Inc.
Sr. Network Analyst
allen.mcclure@yum.com
-----Original Message-----
From: James Bone [mailto:cciehead@yahoo.com]
Sent: Saturday, September 06, 2003 1:37 PM
To: ccielab@groupstudy.com
Subject: RE: bgp to non-bgp to bgp
Ok, I picked up Mr. Halabis BGP book. Im not done reading all of them
as yet. It was doing recursion as it was explained that is why the BGP
route is flapping. More specifically the problem lies in the next hop as
you said, thanks, and as shown below.
routerc#sh ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS
inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
172.16.0.0/24 is subnetted, 2 subnets
C 172.16.20.0 is directly connected, Serial0
B 172.16.1.0 [20/0] via 172.16.1.2, 00:00:33
routerc does not have any info how to get to 172.16.1.2 since the router
between routerc and routerf is only running ospf. I was able to solved
it using static routing.
ip route 172.16.1.2 255.255.255.255 172.16.20.2.
How to solve this another way without using static routing?
Thanks in advance
-----Original Message-----
From: eward15@juno.com [mailto:eward15@juno.com]
Sent: Tuesday, September 02, 2003 1:04 PM
To: cciehead@yahoo.com
Subject: Re: bgp to non-bgp to bgp
Look at your routing table and your BGP table on routera to see where
the next hop is. Chances are the next hop is unreachable, forcing the
BGP entry to time out. The OSPF entry will be placed back into the
routing table, only to give way to the "newly" discovered BGP entry,
continuing the loop.
Eugene Ward
------------------------------------------------------------------------
Hello Group,
I'm trying to understand why this is flapping.
routera --------------routerb--------------------routerc
routera is running BGP in AS 1
routerb is running only OSPF. It cannot run BGP.
routerc is running BGP in AS 2
routera to routerb network is 172.16.20.0 mask 255.255.255.0
routerb to routerc network is 172.16.1.0 mask 255.255.255.0
On routerc, I advertised network 172.16.1.0 under bgp process using
network
172.16.1.0 mask 255.255.255.0
Routera receives the route, 172.16.1.0 and placed in its routing table
as BGP
learned route. However, it disappears every 60 seconds and the route
becomes
OSPF learned route. Eleminating BGP and running only OSPF works but I'm
curious
as to why this is happening. Can anyone explain why? Thanks in advance.
Relevant Configuration follows
routera
ethernet 0
172.16.1.1 255.255.255.0
serial 1
clockrate 64000
172.16.20.2 255.25.255.0
router ospf 10
network 172.16.0.0 0.0.255.255 area 0
************************************************************
routerc
serial 0
172.16.20.1 255.255.255.0
router osp 10
network 172.16.0.0 0.0.255.255 area 0
router bgp 1
neighbor 172.16.1.2 remote-as 3
neighbor 172.16.1.2 ebgp-multihop 2
no auto-summary
************************************************************
routerf
ethernet 0
172.16.1.2 255.255.255.0
router ospf 10
network 172.16.0.0 0.0.255.255 area 0
router bgp 3
network 172.16.1.0 mask 255.255.255.0
neighbor 172.16.20.1 remote-as 1
neighbor 172.16.20.1 ebgp-multihop 2
no auto-summary
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