Remote sites, aggregates and more-specific routes

Tue Dec 7 11:41:16 UTC 2004

Hi,

We currently announce our entire range as the largest possible aggregates. 
We are about to add the first site that's a sizable distance away.

The link to the remote site is relatively expensive, so we don't want to 
have to backhaul traffic between the sites if we can help it.

We seem to have the following options available:

1) Announce the greater aggregate at both ends, and risk having to haul 
traffic between the sites ourselves.

2) Deaggregate our ranges completely. I don't particulary want to do this, 
since the predicted 80/20 split in IP address usage across the sites will 
create a quite a few new routes in the ever growing table.

3) Only announce more-specifics at the remote site, and tag the more 
specific routes NO-EXPORT if we peer with the AS in both locations.

Am I right in thinking that #3 seems is the best option? AFAICS it adds no 
new unnecessary routes to the global table (outside of our immediate peers 
and transit providers) and still keeps unneccessary traffic off of the 
intersite link.

Are there any options I missed?

Sam