From: Peter van Oene (pvo@usermail.com)
Date: Thu Oct 17 2002 - 10:23:54 GMT-3
At 05:32 PM 10/16/2002 -0400, Paglia, John (USPC.PCT.Hopewell) wrote:
>I think the whole basis of this thought has to do with your next-to-last
>sentence.
>
>The 'update-source' command (and correct me if mistaken...like y'all need to
>be told that!!!!) tells the neighbor router specified in the command to
>observe YOUR loopback as the source of the peering relationship. Thus, the
>interface that is being utilized for peering, from the point of view of the
>neighbor, is not directly connected, but is at least 2 hops away, whether it
>be EBGP or IBGP.
>
>I do really think this is outdated but I just thought I'd throw it out there
>and see if anyone knew for sure, and judging from the replies thus far, it
>has to be an 'out-of-practice' practice.
Peering on loopbacks in IBGP is considered best current practises. For
EBGP, it really is simply used as a tool for load balancing in cases where
dual router to router links are used, or where topology necessitates it.
>Thanks,
>John
>
> > -----Original Message-----
> > From: Joe Martin [SMTP:jmartin@capitalpremium.net]
> > Sent: Wednesday, October 16, 2002 4:58 PM
> > To: ccielab@groupstudy.com
> > Subject: RE: EBGP Multihop's necessity with loopback addresses
> >
> > 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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