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Re: AT&T NYC

  • From: alex
  • Date: Tue Sep 03 08:29:35 2002

> > Rubbish again.
> > 
> > *Every* interface that you bring up has a connected route. You redistribute
> > those routes into IGP. You redistgribute statics from that router into IGP.
> > Nail those routes into bgp and set internal community on it. 
> > 
> > network xxx.yyy.zzz.www mask ppp.hhh.ooo.lll route-map set-igp-community.
> 
> So how does this provide equivalent functionality to "compare igp
> metric"? 

First of all, did we agree by now that there is no scalability issue or do
we need to go over this again? 

> I think there are a lot of folks out there who might like
> to do the whole nearest-exit thing.

set metric +1 is your friend.

> Even if you went to the trouble
> of setting up route-maps to your heart's content and managed to get
> each router to prefer paths from the nearest exit router, it wouldn't
> do you much good when a link failure turns that "nearest" into
> "furthest" but the iBGP session stays up.

You metric would be appropriately affected. next-hop-self and confederations
are your friends.
 
> I think maybe the word "need" is being taken a little too seriously
> here. No, you don't NEED a separate IGP to make BGP work. But then
> again, you don't NEED a lot of things to make a network go in its
> most basic form. However, without some of those "unnecessary" things
> you might not find it to perform quite to your liking either. For my
> network, I'd much rather deal with some extra SPF calculations than
> slow convergence and playing route map games to get things like
> nearest-exit working.

There are no route-map games. You can basically have the same route-map on
all internal links. Of course it requires to be able to construct logical
"if then" trees, as well as know some fundamental algebra.
 
> Links and loopbacks => IGP
> Everything else => BGP

IGP trouble -> entire network down with hundreds of otherwise unaffected
customers experiencing connectivity problems and getting hard earned $$
back, sending yet another network into ochapter 11.
 
> But then, nobody ever accused any two engineers of having the same
> personal preferences...
> 
> -c
> 
> 

-- 





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