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  • From: Daniel Golding
  • Date: Thu Aug 29 16:40:35 2002

I wish this was a joke, but I know it's not.

Ralph, they are talking about running BGP as an IGP, not if they are going
to run BGP at all. Most large carriers run BGP everywhere. They also run an
IGP for next-hop reachability within their networks (loopbacks, interface
/30s, etc). The issue was whether you can get away with not running the IGP,
and just running BGP. The problem is, of course, BGP handles many routes
well, and converges relatively slowly. IGPs converge quickly, but only
handle a relatively small number of routes.

If you are offering transit to folks, you need to run BGP pretty much
everywhere. If you are peering, or have multiple transits in multiple
locations, with a network between them, BGP makes a lot of sense. If not,
just run BGP on your edge routers.

As far as an IGP - you need one.

You don't need route reflectors for 5 routers. You probably do need
something at double that number. Use two route reflectors, so if one goes
down, you're ok. Redundancy is wonderful. Or use confederation BGP, which
doesn't usually have single points of failure, but many be a bit too complex
for some networks.

Finally, if cutting and pasting a configuration is making you a "sad clown",
learn Expect or Perl, and write a script. That way, more routers can be
broken in a shorter period of time, leading to greater efficiency.

We now return to our regularly scheduled, low level of signal to noise.

- Daniel Golding

> Ralph Doncaster Said....
> On Thu, 29 Aug 2002, Peter van Dijk wrote:
> > On Thu, Aug 29, 2002 at 01:09:54PM -0400, wrote:
> > > > Has anybody mentioned the benefits of ISIS as an IGP to them.
> > > Link-state protocols are evil, and when they break, they
> *really* break.
> > > I still do not see a compeling argument for not using BGP as your IGP.
> >
> > Slow convergence.
> As well there is the issues of running a full iBGP mesh.  I've actually
> been doing it, and now that I'm about to add my 5th router, OSPF is
> looking a lot better than configuring 4 more BGP sessions.  I've heard
> some people recommend a route-reflector, but that would mean if the
> route-reflector goes down you're screwed.
> -Ralph

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