we have a client connected to two service provider routers through two links ( every link to every SP router). Every SP router have the full BGP internet table. We'd like to send the full BGP table to the client but we'd like to balance the traffic through both links. Could you suggest me the best way to do that? Tks
The first option will not work by default if the two SPs are in different ASes. This is because maximum-path only works for prefixes received from the same neighbor AS by default.
You would need the following hidden command to change this default behavior:
bgp bestpath as-path multipath-relax
This command (along with the maximum-paths x) would cause BGP to select both paths even if they come from different neighbor AS, assuming all other attributes are equals.
taking in account the scalability issues.
router bgp xx
easy to configure but it can be too heavy at level of resource usage
another approach I've seen in the forums is
create two prefix-lists with each that matches one half of IPv4 address space :
provide a bigger local-preference to ISP1 for first half of ipv4 address space and a bigger local preference to ISP2 for the other half of IPv4 address space
prefix-list second-half permit ip 220.127.116.11/1 le 24
route-map ISP1 permit 10
match ip address prefix-list second-half
set local-preference 200
route-map ISP1 permit 20
set local-preference 120
route-map ISP2 permit 10
set local-preference 150
neigh isp1-ipaddr route-map ISP1 in
neigh isp2-ipaddr route-map ISP2 in
Don't expect a fair load sharing with this second method and also return path ratio can be totally different.
Hope to help