[j-nsp] Better distribution of outbound packets

From: Kerry Schwab (Kerry.Schwab@wnco.com)
Date: Tue Oct 09 2001 - 12:19:36 EDT


I currently have BGP set up and running in an environment like so:
   __________________________
  ( )
( Internet )
 ( )
   ==========================
     | |
     | |
     | |
     | <- DS3, Provider | <- DS3, Provider
     | #1 | #2
     | |
 ========= =========
 | M5#1 | | M5#2 |
 ========= ==========
     | |
     ¯---------------------
               | Ethernet Segment
            Firewall(s)
               | 12.5.136.1 == VRRP Address,
        Web/SMTP/etc servers defaults to M5#1
                               12.5.136.19 == M5#1 ip addr
                               12.5.136.18 == M5#2 ip addr
         

We are advertising 12.5.136.0/24 via BGP, and this seems to
work pretty well for inbound packets. Provider #1 and
provider #2 seem to have a good distribution of routes,
and so the inbound traffic seems to be as evenly divided
as I could hope for (60/40 or so).

Additionaly, we seem to able to survive an outage ( DS3, router,
or provider), and the inbound and outbound packets start going
over the surviving line nicely.

But....outbound packets don't seem to be distributed in the same
ratio as the inbound ones. *Some* traffic goes to provider #2,
but the ratio is something like 90/10 ( again, inbound is closer to 60/40).

What appears to be happening:

     The router answering for the VRRP address, where all outbound
     packets are being sent, is counting the ethernet hop to the
     other router as part of the route cost. If I move the VRRP
     address to provider #2's router, the ratio stays close to 90/10,
     but with the "90" now going over provider #2's line.

So... Is there a way to get the router with VRRP running to "subtract"
one hop from the BGP routes it is getting from the other router ?

I am aware of other ways of addressing the problem, but none of them so far
are ideal. ( Both lines on one router, local-pref settings, static routes)

The routers are Juniper M5s.

Thanks !

==
Kerry Schwab
Kerry.Schwab@wnco.com



This archive was generated by hypermail 2b29 : Mon Aug 05 2002 - 10:42:37 EDT