AS path question.

Stefan Fouant sfouant at shortestpathfirst.net
Wed Nov 10 14:44:08 CST 2010


> -----Original Message-----
> From: Jared Mauch [mailto:jared at puck.nether.net]
> Sent: Wednesday, November 10, 2010 3:31 PM
> To: Greg Whynott
> Cc: nanog at nanog.org list
> Subject: Re: AS path question.
> 
> People prepend, and think 'more is better' vs using communities and
> other 'complex' methods of managing their traffic.
> 
> It's also the easy tool from the shed.  'set as-path prepend blah' is
> easier than

In this day and age, I'm still surprised at how many people think AS Path
prepending is the preferred way to influence inbound traffic paths.  As many
providers have default local-pref policies in place which prefer routes
learned from the customer over routes learned from another peer, it is often
the case that a supposed secondary path is actual the preferred path from
the view of that upstream provider.

IMO, a combination of both community tagging to influence localpref coupled
with AS Path prepending on the secondary link is the best approach, and
seems to accommodate both steady state as well as failure scenarios
properly.

Stefan Fouant





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