Sean Donelan writes: | If Sprint isn't pre-pending its routes with Sprint's ASN, who is? Who cares? Maybe more interesting is how is this done? Curious minds want to know. | It is generally considered ill-mannered to use someone else's ASN w | without their permission. Sez who? AS_PATH is a mostly-simple attribute which is used for loop avoidance. Using it as a trail of breadcrumbs is a convenience, but in reality, the only important thing is that eBGP-speakers check "that the autonomous system number of the local system does not appear in the AS path" without discarding the route, although the current draft does point out that eBGP talkers may be configured to use such routes but such a router's "Operations ... are outside the scope of this document". (I would have said "sane analysis", but...) The loops that are avoided are ROUTING ANNOUNCEMENT loops, not forwarding loops. The AS_PATH need have no relation to the way actual traffic will flow when a BGP-speaker selects that route. | Traditionally, pre-pending is done with the pre-pender's own ASN. So, if tradition is so important, why aren't you runing rcp_routed for IDR? | If nothing else, to help track down the party when evil things happen. Sorry, all you can glean from an AS_PATH alone is that your neighbour wants to avoid having the route seen by the things in that AS_PATH. Attributes like AGGREGATOR exist to track parties down, since the AS_PATH cannot be, in some cases. What's your worry here? That someone can stuff your AS into an AS_PATH (personally I'd do it by forming an AS_SET), and thus you can't see a given route? Didn't you follow the ptomaine discussion where exactly that was done to an aggregate? Sean.