From: Peter van Oene (pvo@usermail.com)
Date: Wed Oct 16 2002 - 22:11:10 GMT-3
EBGP packets hit the wire with a TTL of 1 which pretty much makes them link
local. If you want to peer over multiple hops, you need to change this TTL
value which is done using the mulithop command.
At 07:43 PM 10/16/2002 -0400, Paglia, John (USPC.PCT.Hopewell) wrote:
>Thanks for the reply. Actually, I am not having a problem. I was just
>wondering about something someone told me. I never have configured 'ebgp-mu'
>for connected neighbors, but this person said 'you need it if using
>'update-source loop 0' because loop 0 isn't directly connected to the
>neighbor.'
>
>I just wanted to know if anyone else has heard of such madness. I've never
>configured BGP like this and it has never been a problem.
>
>Thanks,
>John
>
> > -----Original Message-----
> > From: Rem [SMTP:rem@digdomsol.com]
> > Sent: Wednesday, October 16, 2002 7:27 PM
> > To: Paglia, John (USPC.PCT.Hopewell)
> > Subject: RE: EBGP Multihop's necessity with loopback addresses
> >
> > Are you running an igp between those neighbors?
> >
> > Where ebgp-multihop comes into play is between neighbors that are not
> > directly connected and run only ebgp between them, ie your 2 loopback
> > interfaces. if you run a trace between these 2 while running only ebgp you
> > will see that they will not be able to perform a tcp connection, that is
> > because the loopbacks do not know how to get to the remote side. if an igp
> > is running between your serial connection then the route is established
> > and
> > the tcp connection can occur.
> >
> > try removing any internal routing protocol from your tables and see if it
> > drops the connection. it has been my experience that this is currently the
> > case and i know from experience that it has been a problem. watch out for
> > it
> > on the test when your start redistributing and the igp route goes away and
> > all of a sudden your bgp drop also. its a nasty little thing if you don't
> > see it coming.
> >
> > hth
> > Ross
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> > Paglia, John (USPC.PCT.Hopewell)
> > Sent: Wednesday, October 16, 2002 1:01 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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