Prepending with another ASN you don't own

Rubens Kuhl rubensk at
Fri Dec 16 10:13:50 UTC 2016

Even in that case I believe you should encapsulate between two instances of
your own ASN. Your example follows this but the text says only about the
last one in the path, while having both last and at least one previous is
better since you won't be implying that some other AS has connection to yet
another AS, it's just you doing this.


On Thu, Dec 15, 2016 at 4:54 PM, Andrew Imeson <andrew at>

> 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
> another
> continent.
> Solution:
> Prepend at the geographically-distant PoP so that the AS path looks
> like <ACME> <BAD-ISP> <ACME>, and thus that service provider
> (<BAD-ISP>)
> 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
> this
> be "bad?"
> --
> Andrew Imeson
> andrew at

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