[c-nsp] BGP load balancing (outbound)

[Andrew Tolstykh]

Based on your configuration (Multi-homed to two ISPs through a single router) you can only do load sharing (the following configuration guide uses weight to accomplish this).

http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a00800945bf.shtml

In this scenario, load balancing is not an option in a multihomed environment, so you can only do load sharing. You cannot do load balancing because BGP selects only a single best path to a destination among the BGP routes that are learned from the different ASs. The idea is to set a better metric for the routes in the range 1.0.0.0 to 128.0.0.0 that are learned from ISP(A) and a better metric for the rest of the routes that are learned from ISP(B).

HTH,
Andrew

On 18/05/2010, at 12:42 AM, Andrew Tolstykh wrote:

> Just a shot in the dark, but I don't see load balancing enabled in your configuration snippet:
> 
> router bgp xxxxx
> maximum-paths 2
> 
> HTH,
> Andrew
> 
> On 17/05/2010, at 11:52 PM, amps wrote:
> 
>> Scenario:  6509-3BXL receiving 2 full tables.
>> 
>> Problem:  Outbound traffic imbalance
>> 
>> Feed 1 (AS1 in this example):  Direct to tier-1 provider
>> Feed 2 (AS2 in this example):  Colo/house 'mix' of about 5 providers
>> 
>> Outbound traffic pretty much all goes out feed 1.  BGP tables from each
>> provider are nearly identical, so the router is either choosing the lowest
>> router-id, or shortest BGP path..even if I prepend the inbound on feed 1 I'm
>> still seeing most/all traffic leave feed 1... any advice on getting traffic
>> to balance without static route-maps?  I'm perfectly happy if odd/even AS's
>> were pref'd to one or the other...anything BGP based.  Regex on the inbound
>> route-maps?  Example of something that might work?
>> 
>> Thanks in advance...
>> 
>> ##Current config:
>> 
>> router bgp xxxxx
>> no synchronization
>> bgp log-neighbor-changes
>> bgp update-delay 90
>> redistribute static route-map STATIC-TO-BGP
>> neighbor x.x.x.1 remote-as 1
>> neighbor x.x.x.1 soft-reconfiguration inbound
>> neighbor x.x.x.1 prefix-list ADVERTISE out
>> neighbor x.x.x.1 route-map TRANSIT-1-IN in
>> neighbor x.x.x.1 route-map TRANSIT-1-OUT out
>> neighbor x.x.x.2 remote-as 2
>> neighbor x.x.x.2 soft-reconfiguration inbound
>> neighbor x.x.x.2 prefix-list ADVERTISE out
>> neighbor x.x.x.2 route-map TRANSIT-2-IN in
>> neighbor x.x.x.2 route-map TRANSIT-2-OUT out
>> no auto-summary
>> 
>> route-map TRANSIT-1-IN permit 10
>> set as-path prepend last-as 1
>> !
>> route-map TRANSIT-1-OUT permit 10
>> set as-path prepend xxxxx
>> !
>> route-map TRANSIT-2-IN permit 10
>> !
>> route-map TRANSIT-2-OUT permit 10
>> !
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>