[j-nsp] Set weight (BGP attribute) in JunOS

[Jeff Wheeler]

On Sun, Nov 25, 2012 at 4:56 AM, Mihai <mihaigabriel at gmail.com> wrote:
>  Weight is a Cisco proprietary thing and cannot be used with a Juniper
> device. Maybe you could use preference (not local-preference).

"preference" in JUNOS is like administrative distance on IOS.  It's
probably a good idea to mention this when suggesting its use as a
substitute for "weight" because it is conceptually different.  Like
weight, though, it is possible to make your iBGP domain produce
unusual results if you fool around with preference.  Unlike
local-preference, these changes are not signaled to iBGP neighbors.
In a network like:

A---B---C

If you alter preference on router B, it is possible that router A will
send packets for a prefix which it thinks will exit the network at
router C, but in fact, router B has made a different bestpath
selection and picked its own neighbor as the egress for that prefix.
This may make the network confusing to troubleshoot.  If you had BGP
customers who weren't stupid, it would anger them.  If you have
labeled-unicast it would not happen though.

--
Jeff S Wheeler <jsw at inconcepts.biz>
Sr Network Operator  /  Innovative Network Concepts