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Re: AT&T NYC

  • From: Jesper Skriver
  • Date: Tue Sep 03 11:39:40 2002

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.




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