From: victor wu (vkwu@attcanada.ca)
Date: Sat Nov 30 2002 - 19:21:10 GMT-3
The update-source is meant primarily for iBGP peering. It is used to
replace the next-hop address of a route learned from an eBGP neighbor with
the
iBGP own address. For example R1 and R2 and iBGP peers and R1 also has eBGP
session
with R3. When R1 learns a route from R3, the next hop of that route is R3
address.
Without the "update-source", R1 would advertise that route to R2 with the
next hop being
the R3 address but R2 may not know how to get R3 address.
Hope that helps.
----- Original Message -----
From: "Peter van Oene" <pvo@usermail.com>
To: "Nathan Chessin" <nchessin@cisco.com>
Cc: <ccielab@groupstudy.com>
Sent: Saturday, November 30, 2002 9:37 AM
Subject: Re: BGP and Loopback
> Unless Cisco has changed their default behavior wrt to how BGP packets
> are generated for IBGP peering, without this command, your IBGP peers
> should not become established due to source/destination mismatches.
> This assumes you are peering on loops however.
>
>
> On Sat, 2002-11-30 at 01:38, Nathan Chessin wrote:
> > Hi All,
> >
> > I am finding that it is not necessary to use the "update-source" for
iBGP
> > peering. Can anyone verify this? I thought the update-source command
said
> > what interface the updates were coming out of, but it doesn't seem to
matter
> > as long as there is a route back to that interface.
> >
> > For that matter, it doesn't seem necessary for eBGP either. Is this an
old
> > command that isn't necessary anymore?
> >
> > Thanks,
> >
> > Nate
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