The biggest issue with using a heavy hammer to effect traffic is that you don't always know why the other side is routing the way they are. Could be simple cost (peer vs transit) or a larger issue like congestion. Either way think before you route. I'm thinking Pandora's box hasn't just been opened but blown apart..... -jim On Sat, Aug 30, 2008 at 2:55 AM, Florian Weimer <fw@deneb.enyo.de> wrote:
* jim deleskie:
Announcing a smaller bit of one of you block is fine, more then that most everyone I know does it or has done and is commonly accepted. Breaking up someone else' s block and making that announcement even if its to modify traffic between 2 peered networks is typically not looked as proper. Modify your taffic good. Do it to anyone other traffic = bad.
No, the idea would be to do this to your own prefixes/traffic.
+------/AS 2/-----/AS 3/--------+ | | /AS 1/ /AS 4/ | | +----------/AS 5/---------------+
I'm AS 1, and the link to AS 2 has a bad metric from my POV. AS 4 uses local preference (or something else I can't override by prepending my own AS) to route traffic to me through AS 3 and AS 2. Now I prepend AS 4 to my announcement to AS 2, and voilà, the traffic flows through AS 5, as desired.
No prefix hijacking has occurred (I would have received the traffic anyway, just over a different path), it's just traffic engineering. (But probably a variant that is generally frowned upon.)