BGP Route Issues

Mon Aug 19 03:10:26 UTC 2013

On 8/18/13 6:33 PM, Christopher Karel wrote:
> 
>     I'm hoping you guys might be able to offer some advice or insight
> into a BGP problem I've got.  I've noticed some strange routes between
> our network, AS27270, and AS22943.  It looks like both our networks are
> dual homed.  One ISP as the primary, and the other used as a backup,
> with path prepending to prevent it from actually being used except in an
> outage.  However, our route to 22943 appears to be using their backup
> link.  (27270 4323 7018 22943 22943 22943 22943 22943 22943 22943 22943
> 22943 22943 22943)  Which is strange, because we can reach their primary
> ISP without any such rigmarole.

It's not strange. AS path prepending like a typewriter monkey on crack
doesn't mean anything and certainly does not a "backup" link make.
Localpref can and will make it the best path anyway.

~Seth