From: Michael Popovich (m.popovich@xxxxxxxxx)
Date: Sat Jul 06 2002 - 08:23:22 GMT-3
I have seen this happen before in my lab with IBGP. While I questioned
why it was up and still remembered to configure update source on the
routers because it is not consistent. Things like this tend to happen
sometimes just make sure you know the right way to do it and why.
MP
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Hunt Lee
Sent: Friday, July 05, 2002 11:54 PM
To: ccielab@groupstudy.com
Subject: BGP Command Q
Group,
I have a BGP question and the scenario is as follows.What am i doing
wrong ? Scenario is:
RTA -- RTB -- RTC
They are all in the same AS 1.
RTA's Serial: 10.1.1.1
RTB's Serial: 10.1.1.2 (connecting to RTA)
RTB's Serial: 10.1.2.1 (connecting to RTC)
RTC's Serial: 10.1.2.2
Each Router also has a Loopback Interface for IBGP connection.
RTA's Loopback0: 172.16.1.1
RTB's Loopback0: 172.16.1.3
RTC's Loopback0: 172.16.1.2
Ok - what I am confused is the BGP command "neighbor x.x.x.x
update-source <interface x>"?? My understanding of the command is
that the router who used this command can specify another interface
to be used for IBGP Neighbor connections.
So at here, RTA will tell RTB (172.16.1.3) to use RTA's Loopback
interface for IBGP session.
RTA:-
router ospf 1
log-adjacency-changes
network 10.1.0.0 0.0.255.255 area 0
network 172.16.1.1 0.0.0.0 area 1
!
router bgp 1
bgp log-neighbor-changes
network 1.0.0.0 mask 255.128.0.0
neighbor 172.16.1.3 remote-as 1
neighbor 172.16.1.3 update-source Loopback0
RTB:-
router ospf 1
log-adjacency-changes
network 10.1.0.0 0.0.255.255 area 0
network 172.16.1.3 0.0.0.0 area 3
!
router bgp 1
no synchronization
bgp log-neighbor-changes
neighbor 172.16.1.1 remote-as 1
neighbor 172.16.1.1 route-reflector-client
neighbor 172.16.1.2 remote-as 1
neighbor 172.16.1.2 update-source Loopback0
neighbor 172.16.1.2 route-reflector-client
But at RTB, there is no neighbor update-source statement pointing
back to RTA. Nevertheless, the BGP session still managed to get
established. How can BGP still managed to establish the BGP
connection??
RouterB#sh ip bgp summary
BGP router identifier 172.16.1.3, local AS number 1
BGP table version is 3, main routing table version 3
2 network entries and 2 paths using 266 bytes of memory
1 BGP path attribute entries using 60 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP activity 4/4 prefixes, 4/2 paths, scan interval 15 secs
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down
State/PfxRcd
172.16.1.1 4 1 15 13 3 0 0 00:03:52 1
172.16.1.2 4 1 14 14 3 0 0 00:04:17 1
RouterB#
Or is this command only required for EBGP sessions? Anyone with
ideas.
=====
Thanks in advance for ur time and replies.
Hunt
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- Find yourself a bargain!
This archive was generated by hypermail 2.1.4 : Sat Sep 07 2002 - 19:36:20 GMT-3