At 10:37 AM 7/12/96 -0400, Paul Ferguson wrote:

At 07:40 AM 7/12/96 -0600, Forrest W. Christian wrote:

...

However, the world never needs to see this - it's an internal routing issue and when the internal route flaps it shouldn't affect the external routes.

So in summary:

1) Never flap your routes in public. What you do in your own home is your own business.

I'm sorry, but I'm afraid that you're missing the point here.

In most larger ISP backbones, the behavior of their IGP is indeed visible to the public, since in most instances, most of the Internet traffic relies on the stability of these interior (an esoteric term) networks. Therefore, whether interior or exterior flap is really of no relevance in this context.

I think the real difference is this. If my routes are only seen at one place then it makes sense for me to announce them whether or not I can actually get to them. If, however, it is possible to get to parts of my network from one exchange, but not another then the routes should only be announced where they can actually be gotten to from (obviously). I.e. if I am a small to mid-sized provider who has multiple t-1's to the net to different providers, and then those t's come into the same physical network (either the same router or one's that are topologically adjacent to one another) chances are good that if one of those routers can't get to part of my network the other probably can't either. In this instance it makes sense for me to null0 the routes and do my part to not affect instability (only routes which originate in my AS though, if I have any multihomed downstreams then they would not want me announcing their routes when I can't get to them). If, however, I have a network which has multiple egresses to the internet at large it is very possible for one part of my network not to be able to reach certain sites while other parts can. I would then want to "announce my instability" so that I am only announcing networks where they can actually be reached from. Justin "Long babbling posts R us" Newton Justin Newton Internet Architect Erol's Internet Services