FW: BGP Load Sharing

Sat Sep 18 09:02:36 UTC 2004

Chris,

My comment inline.

-----Original Message-----
From: owner-nanog at merit.edu [mailto:owner-nanog at merit.edu]On Behalf Of
Chris Strandt
Sent: Friday, September 17, 2004 8:40 PM
To: nanog at merit.edu
Subject: BGP Load Sharing

I am hoping to learn from the great pool of experience on this list.

We currently have 2 OC3 connections going to 2 seperate providers.  We
are using netflow statistics to balance our traffic flows (which
outgoing is our major concern).  Flow tools, snmp output, some custom
scripts, and some bgp weighting does the trick.

We are in the process of upgrading to Cisco 12012 GSRs, and adding
additional connectivity.  We need to find something we can use to do the
same type of thing on the 12012 GSR.  The custom scripts work fine.. but
it appears some line cards don't support netflow.

1) Is there an open source software that will assist us in load sharing?
2) Are there specific cards we need for netflow on a 12000 series? Is
the difference based on Line Card Engine (0,1,2,3,etc)?
3) Is there an alternate way to control outgoing traffic flow to
multiple upstreams using bgp (besides splitting the address range up and
blindly pointing chunks to each provider)?

>>> What you advertise to upstreams affects incoming traffic, not outgoing.
What upstreams advertise to you and the policies you employ on those routes
affects outgoing. One basic technique is to decide roughly how much outgoing
traffic you want going over each link, then look at how your current
outgoing traffic is split (e.g., 70% via ISPA, 30% via ISPB) then manipulate
the Local Preference attribute on some of the routes you're receiving to
achieve roughly the balance you're looking for.

Mike McSpedon
Arrow Global Data Communications
Arrow Electronics, Inc.
50 Marcus Drive
Melville, New York 11747
Phone: 631.847.5551

Thanks,
-Chris Strandt
Liquid Web Inc