RE: Route aggregation w/o AS-Sets

Suppose you had a set of customers than all announced to you a set of routes
and all those routes complete an aggregate
and you announce only the aggregate to those customers
and you include an AS_SET with it
then those customers will drop your aggregate, thinking there is an AS-loop
and those customers will not be able to reach each other.

An AS_SET does not prevent routing loops and can prevent correct routing.

But you must include the ATOMIC_AGGREGATE attribute, so that someone else
does not disaggregate your aggregate that does not have the AS_SET.


I apologize if I wasn’t clear.

I don’t recommend ever using AS_SET.

So, in rule 3, I use the atomic-aggregate knob
to announce the single covering aggregate with
my backbone ASN as the atomic-aggregate origin
AS, and I don’t generate or propagate any AS_SET
information along with the aggregate.

That way, no loop is seen by any of the downstream
networks that are announced the aggregate prefix.

I hope that helps clear up what I meant in my third
rule. :slight_smile:



Sorry, I did not intend to imply that you were.

I should have prefaced my post with “to add”.