[c-nsp] Re: [j-nsp] load balancing between multiple BGP links

[Chris Morrow]

On Wed, 14 Sep 2005, sin wrote:

> Alok wrote:
>> It isnt juniper in my case though but I just remebered the per packet thing
>> when I ran into this with another vendor
>>
>> however, even link bandwidth via BGP , which i perhaps remember has been
>> there since 5.6 doesnt consider the "immediate util" at the time of
>> transmitting the packet....
>>
>> Perhaps "per packet" with BGP link bandwidth would be good infact  i think..
>> .
>> or perhaps for flow based, flow setup based on "actual util at the time of
>> setup".... though nothing still seems to beat per packet :-) with link
>> bandwidth i guess...
>>
>
> i know that with cisco you can setup an acl that can match even/odd ip
> addresses and then use that acl in a route map to distribute the traffic
> across two links to another bgp speaker (that in it's turn can do the
> same with the link back to you). this might be an option for you.

uhm, I'm positive another person mentioned this before, but your IGP does 
the loadbalancing, so get some form of IGP to tell you that the 2 links 
are available for the same destination next-hop and be done with it. 
Policy routing is just so not a solution...

Example, your bgp neighbor is over 2 links, static route the /32 across 
both links and reset the next-hop to neighbor IP for all inbound routes 
(this should be the default, but with multihop ebgp the neighbor can send 
you an alternate next-hop so you should reset it for your own protection).

When traffic is sent to the next-hop it'll get automagically loadshared 
across both links... in a 'per flow' way, so it's not 50/50 more like 
45/55 to 70/30.