Prepending with another ASN you don't own

Andrew Imeson andrew at
Thu Dec 15 18:54:34 UTC 2016

Is it acceptable to prepend using another networks ASN as long as your
ASN is the last one in the path? I can think of a few scenarios where
this is helpful.

One scenario: Anycast content provider with an ISP (who you aren't
directly peering with) is choosing to send all traffic to a PoP on

Prepend at the geographically-distant PoP so that the AS path looks
like <ACME> <BAD-ISP> <ACME>, and thus that service provider
views it as a routing loop and chooses one of your other PoPs. Sure
there are better solutions like communities, but why (if it is) would
be "bad?"

Andrew Imeson
andrew at

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