No. I was talking about this only being configured
on the RouterA/Routerb pair Where that represents
it's own nontransit AS.
That's why I asked what deployment scenarios
are most of you asking about for this.
I see this more as a benefit for a stub AS
rather than any AS that is transit.
AS1 AS2
> > ISPA ISPB
> > | |
> > RouterA --- IBGP --- RouterB
|---------- AS3 --------|
I put in the proposal the next hop check but
are you asking that is a less specific prefix
exist in the RIB then just dont' install a more
specific regardless of how/where that less specific
was learned?
Rodney
On Wed, Dec 01, 2004 at 08:59:13AM -0500, lee.e.rian at census.gov wrote:
>
> On 11/30/2004 10:30 PM, Rodney Dunn <rodunn at cisco.com> wrote:
>
> > I'm trying to put it together in my head
> > how it would be done for dual EBGP sessions.
> >
> > ie:
> >
> > ISPA ISPB
> > | |
> > RouterA --- IBGP --- RouterB
> >
> > Say I get a /16 and a /24 for a prefix from ISPA with
> > the same next hop so I wouldn't want to install the
> > /24. But what happens if I get a /16 from ISPB and
> > that gets sent to RouterA. That prefix would have
> > a next hop of Router B or ISPB so it would be a different
> > prefix and installed in the RIB. Now the traffic that
> > was originally flowing to the /24 would take the backup
> > path (due to a longest match lookup) rather than the
> > path it would have taken if we had installed the original
> > /24. Would that be acceptable?
>
> I think not.
>
> Say RouterA advertises a /16 and a /24 within the /16 to ISPA, RouterB
> advertises the same /16 and a different /24 within the /16 to ISPB.
>
> If I'm understanding the proposal correctly, ISPA drops the /24 since it
> has the same next hop as the /16. ISPB also drops their /24 since it has
> the same next hop as the /16. If the link between RouterA and RouterB goes
> down then ISPA, and all their customers, aren't going to be able to get to
> siteB (the /24 advertised by RouterB) while ISPB, and all their customers,
> aren't going to be able to get to siteA (the /24 advertised by RouterA).
>
> Lee
>