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
Chris, My comment inline. -----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu]On Behalf Of Chris Strandt Sent: Friday, September 17, 2004 8:40 PM To: nanog@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)? 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