I suppose so because prepend is so easily defeated, but sometimes you don't own a prefix shorter than the one you need to advertise. Assuming I understand your suggestion correctly. 2011/12/15 Holmes,David A <dholmes@mwdh2o.com>
For this very reason I have advocated using longest prefix BGP routing for some years now, and checking periodically for the expected path, as it became obvious from investigating traceroutes that traffic was not being routed as intended using AS prepends.
-----Original Message----- From: Keegan Holley [mailto:keegan.holley@sungard.com] Sent: Wednesday, December 14, 2011 10:08 PM To: NANOG Subject: local_preference for transit traffic?
Had in interesting conversation with a transit AS on behalf of a customer where I found out they are using communities to raise the local preference of routes that do not originate locally by default before sending to a other larger transit AS's. Obviously this isn't something that was asked of them and it took a few days to find since the customer is not a large company and neither them nor my company has a link or business relationship with the AS in question. This seemed strange to me for obvious reasons, but I was curious if anyone else was doing this and why. You obviously cannot use prepend to affect transit traffic again for obvious reasons. MED is a weak metric but it at least only affects traffic that was already going to transit your AS. The larger transit AS was favoring a lower bandwidth link for the customer and causing them to drop packets mysteriously. Just wondering if this practice seemed as strange to others as it does to me.
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