[51644] in North American Network Operators' Group
Re: AT&T NYC
daemon@ATHENA.MIT.EDU (Jesper Skriver)
Tue Sep 3 11:38:10 2002
Date: Tue, 3 Sep 2002 17:36:30 +0200
From: Jesper Skriver <jesper@skriver.dk>
To: Iljitsch van Beijnum <iljitsch@muada.com>
Cc: nanog@merit.edu
Mail-Followup-To: Jesper Skriver <jesper@skriver.dk>,
Iljitsch van Beijnum <iljitsch@muada.com>, nanog@merit.edu
In-Reply-To: <20020903172204.W80168-100000@sequoia.muada.com>
Errors-To: owner-nanog-outgoing@merit.edu
On Tue, Sep 03, 2002 at 05:26:54PM +0200, Iljitsch van Beijnum wrote:
> On Tue, 3 Sep 2002, Jesper Skriver wrote:
>
> > > Links and loopbacks => IGP
>
> > Why on earth does you want your link addresses in your IGP ?
>
> > Sometimes it cannot be avoided, due to bad implementation, but why
> > do you need it ?
>
> Routers that learn a route over IBGP need to know where the next hop
> address for route from other AS points to. Since this can't be a
> loopback address and you typically don't run an IGP on subnets between
> border routers in your AS and a remote AS, you need to either set
> next-hop-self on all IBGP sessions or redistribute connected in your
> IGP.
Yes, next-hop-self on iBGP sessions is a way to ensure that all BGP
routes have a loopback address as next-hop.
This also solve nasty issues with IXP's, and someone advertising a more
specific of the peering LAN prefix.
/Jesper
--
Jesper Skriver, jesper(at)skriver(dot)dk - CCIE #5456
Senior network engineer @ AS3292, TDC Tele Danmark
One Unix to rule them all, One Resolver to find them,
One IP to bring them all and in the zone to bind them.
