From: Joe Martin (jmartin@capitalpremium.net)
Date: Wed Oct 16 2002 - 17:58:19 GMT-3
If you use a local interface or a physical interface ip address in your bgp
neighbor statement then you would lose your peering if the interface or
network goes down, even if there is another route to the bgp neighbor. this
is why it is suggested that you use the loopback ip as your update source
and specify the loopback address in your neighbor statements. This way, if
your direct connection to your bgp neighbor goes down you can still maintain
the neighbor relationship. However, now your neighbor is not neccessarily 1
hop way. So this is where the ebgp multi-hop command comes in.
Someone correct me if i'm wrong.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Paglia, John (USPC.PCT.Hopewell)
Sent: Wednesday, October 16, 2002 2:01 PM
To: 'ccielab@groupstudy.com'
Subject: EBGP Multihop's necessity with loopback addresses
I recently heard that if you are establishing your BGP neighbors using
'update source loopback 0', you should also use the 'ebgp-mu' cmd, even if
the neighbors are directly connected...the reason being that your loopback
is NOT directly connected to the neighbor. However, in my experiments I have
never done this for neighbors that are directly connected, yet have
established peerings successfully.
Is there validity to this statement, and if so, under which circumstances is
it absolutely vital, other than the 'non-physically or nbma topology'
scenarios??? Something tells me that this may be an older IOS issue or
something like that.
John
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