On Tue, Feb 19, 2008 at 12:41:14AM -0300, Eduardo Meyer wrote: > On Feb 18, 2008 8:47 PM, Dustin Lundquist <[EMAIL PROTECTED]> wrote: > > To balance your inbound you can prepend your AS number to your > > advertisements to depreference them. Some larger ISPs do this on a per > > prefix basis, but since a sizable portion of ISPs are running Cisco gear > > with a 256K prefix limit it is not advisable to create additional > > prefixes for the purposes of traffic balancing. > > > > For outbound, its easier you can use local preference. For reference > > here is the Cisco BGP path selection process, OpenBGPD is similar: > > http://www.cisco.com/warp/public/459/25.shtml > > > > > > Dustin Lundquist > > Right, I could define the preffered outbound traffic to a certain AS > with localpref. However, I could not balance it, and did not find how > I am supposed to. > > For example, I have a certain traffic outgoing to AS 4230, it was > going via AS17379, and with localpref I could make it go via 18881. > > However, I need to balance it in the adequated ratio, say, make 40% of > outgoing traffic to 4230 go via 1881 while 60% goes out via 17379. > > If you could point me to what to read, or suggest anything, thats what > I need, some words from the experienced ones. >
You can not do load balancing between upstreams on a single prefix. This is just not possible. You can use filters and localpref to toss prefixes to a specific upstream. Correctly balancing traffic with bgp is the high art of network engineering. Most of the time you need to try a bit until you're happy. One hint don't try to build up prefect rules one week from now the world will look different and your rules may probably backfire on you. Try to make a few broad rules, e.g. match from $PEER source-as 4230 prefix 189.0.0.0/8 set localpref 300 Last but not least monitor your traffic and figure out which traffic goes over which link. -- :wq Claudio
