Hello Experts,

A client has a BGP load balancing issue. They are multihomed to different providers, and use route-maps matching as-paths to allow routes from specified ASs in, as follows (details altered to protect identities):

ISP1

neighbor 1.1.1.1 remote-as 111

neighbor 1.1.1.1 route-map allow-from-isp1 in

ISP2

neighbor 2.2.2.2 remote-as 222

neighbor 2.2.2.2 route-map allow-from-isp2 in

route-map allow-from-isp1 permit 10

match as-path 11

route-map allow-from-isp2 permit 10

match as-path 22

ip as-path access-list 11 permit _111_[0-9]*

ip as-path access-list 11 permit _112_[0-9]*

ip as-path access-list 11 permit _113_[0-9]*

ip as-path access-list 11 permit _111_[0-9]*_[0-9]*$

ip as-path access-list 11 permit _111_[0-9]*_[0-9]*_[0-9]*$

ip as-path access-list 22 permit _221_[0-9]*

ip as-path access-list 22 permit _222_[0-9]*

ip as-path access-list 22 permit _223_[0-9]*

ip as-path access-list 22 permit _222_[0-9]*_[0-9]*$

ip as-path access-list 22 permit _222_[0-9]*_[0-9]*_[0-9]*$

(in reality there are more entries in the as-path list)

ip route 0.0.0.0 0.0.0.0 FastEthernet2/0 200 (this is connected to ISP1)

I would consider this set up to be partial routing with a primary default route(??). The questions that I have are as follows:

1) A disproportionaly large amount of traffic is being sent to ISP1 (incoming is roughly equal). I think that this is because of the default route, even though the routing table has hundreds of routes in it - do you think this is likely? If not, what would be a more likely cause?

2) It's my understanding that this solution doesn't offer any redundancy - for instance, if peering with ISP2 is lost, these routes would not be permitted via access-list 11 to be advertised to the router and installed in the r-t. Is this correct?

Your help would be most appreciated.

Thanks,

J