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

[Jeff Wheeler]

On Sun, Nov 25, 2012 at 6:29 PM, Ali Sumsam
<ali+junipernsp at eintellego.net> wrote:
> Actually I am working on migration from Cisco to Juniper.
> On Cisco router weight attribute is used and have to set same preference
> same on Juniper.
>
> Thats where I found that there is no weight in Juniper.
> Good to know some thing :).

I think you mis-understood the information you read in the
documentation that Ytti referenced.  Please see my earlier post on
this thread.  I will expand on it since you must not have gotten it
clearly.

On IOS, Weight is an attribute you can use to basically override the
whole BGP bestpath selection process, and pick a path you want.  This
is a double-edged sword.

If you use Preference1 on Junos to get the same effect you will
sometimes have results that are different than you expect.  Like I
mentioned before, Preference1 on Junos is the same concept as
Administrative Distance on IOS.  You usually use it to make one
routing protocol, or type of route, have better bestpath selection
than another.  For example, if you configure "distance" under "router
bgp ASNXX."

This matters because if you were to pick Preference1 = 100 for a
route, and the rest of  the configuration was basically the default,
that route would be selected in favor of OSPF type E routes, which
normally have Preference1 = 150.  You might use such routes for
learning 0/0 inside your network, etc.

I think this is important for you to know before you finish your
project.  Otherwise, it may cause confusion later that you are not
equipped to troubleshoot!

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