On Wed, Oct 08, 2008 at 09:14:02AM +0200, BARDOU Pierre wrote: > > Hello, > > Failover already works with BGP on my test conf, the problem is that BGP > only selects ONE route to a destination, so there is no load balancing. >
There is loadbalancing insofar that if you have two independent upstreams you get two different views of the internet and you should be able to split the 250k IPv4 routes into two sets that will result in equal use of both links. This is the usual traffic engineering done on BGP with the help of match filters that change the localpref based on communities, AS pathes or whatever you like. > The easiest for me would be to tell BGP to keep TWO routes to each > Destination, and use them in a round-robin way. > > That's what Cisco does with BGP multipath > http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094431 > .shtml#bgpmpath > This will not work as you expect. In your setup case with two independet upstreams only one upstream will be selected. >From the document: In order to be candidates for multipath, paths to the same destination need to have these characteristics equal to the best-path characteristics: * Weight * Local preference * AS-PATH length * Origin * MED * One of these: o Neighboring AS or sub-AS (before the addition of the eiBGP Multipath feature) o AS-PATH (after the addition of the eiBGP Multipath feature) In your case neither the Neighboring AS nor the AS-PATH will be the same. This is the main reason why I never spent time to allow multipath selection in bgpd. It will only work in very few setups. -- :wq Claudio
