Chris Adams wrote on 11/02/2020 17:30:
Just curious what others do... I always assumed AS path filtering to customer (and their downstream customers) AS was a standard best practice.
It is. Then again, there exists every exception to the rule you can think of. If the exception has not been seen yet, we have not looked hard enough. => I.e. it depends. Is my answer. BCP is to not accept direct customer routes 'another provider's AS in the path'. If you can reach an agreement with the customer. You can agree to a >standardized< exception for this single customer. <= Your dice to roll. You are the customers upstream in this case. AS-path rewriting on the customers side of the eBGP connection is an option. If they remove $otherProviders ASN from the path before (re-)announcing the black-hole routes to you. So $customerASN is seen as the source when you receive the announcements. Chriztoffer