Hi guys,
I’ve two upstream providers (and use BGP) and I can want to modify the route to my network, I want to prefer ISP 1 to be used to access my networks instead of ISP 2. I set prepend 6 times in ISP2, so according to that logic ISP 1 should be used, but it’s not!!! I did some looking glass test in lg.he.net and noticed that ISP2 has a higher LocPref (100) vs 70 of ISP1…is there any way to modify that, so ISP 1 will be used instead of ISP 2?
Thanks,
Yes. Get a copy of HE’s bgp communities policy document.
Make sure that your BGP session is configured on their end to send and receive communities.
Once this is done, and you know which community affects the localpref on HE’s side, apply that community to your outbound advertisements to HE. Whichever out-filter rule is currently prepending x6, you can replace the prepend statement with the action to set the community = xx:yy for dropping your local_pref on HE’s side.
You will not need to use as-prepending because if HE prefers their peer routes above their direct connection to you, then they won’t propagate your announcement unless your connection to ISP1 goes down. (this can be a bit slower to converge, though, so do be aware your failover is going to be slightly more noticeable)
As it stands, the traffic entering via HE is probably only originated on-net. With AS_PATH_LENGTH of 7 by the time it’s in the next networks, nobody’s going to route via HE unless that’s their only provider, or their localpref favorite.
If their localpref community doesn’t support dropping lower than 70, you’ll need to drop to 70 AND do some prepending, at LEAST as many times as it takes to make their routes via other carriers be 1 path shorter.