BGP -Maximum Paths [7:6887]
Hey gang, I have a question on maximum-paths in BGP; This is the scenario: 4 T1's running EBGP to our ISP in a multihome peer session; each of the circuits go to a different POP. Each of the peer sessions receive a partial routing table from our provider. What we have found is that load sharing (outbound to our ISP) is virtually non-existant. well, i'm studying for BCSN and came across the maximum path feature, and it seems like the solution. My question is this: we have enabled maximum-path 4 to load share between the four sessions. This, however has had a neglible effect. Does the fact that we still hear routes from the provider from different pops affect this? In other words, since the 4 pops are in a different geographical area, and therefore may send a different bgp table which in turns overrides the maximum path command. I want to try having the provider send a default route instead; the thought being that our router will not have to decide on best paths, and leave that to ISP router, but the powers to be don't want that (for some reason...) Does anyone have any suggestions? thanks all, moe _ Get your FREE download of MSN Explorer at http://explorer.msn.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=6887&t=6887 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: BGP -Maximum Paths [7:6887]
BGP multi-path only works with *identical* prefixes, the only difference between the paths permitted is the router-ID of the originating router. Are you certsin that you are receiving identical routes from all the PoPs? If you have four T-1s I would suggest that before worrying about load-balancing, you seriously look at resilience in your uplink - ie split your T-1s out over at least one other router. As far as load balancing goes, and assuming that the PoPs are all pretty equally connected, it is up to you how to weight the routes. A really basic, semi-arbitrary way might be to match as-paths on each link as transiting each of the top 4 Tier-1s: UUNet - AS701 C&W - AS 3561 AboveNet - 6461 BBN - AS1 (not sure my details are entirely up to date, but open to comment) and the set the local-preference to >100 for these paths on each router this might be a starting point - it is a coarse grained way to split the traffic, you can fine-tune from there. it may be worth checking those AS-paths on each router to see whether any one of the four is best connected to those routes. hth Andy - Original Message - From: "moe humm" To: Sent: Saturday, June 02, 2001 5:01 PM Subject: BGP -Maximum Paths [7:6887] > Hey gang, > > I have a question on maximum-paths in BGP; > > This is the scenario: 4 T1's running EBGP to our ISP in a multihome peer > session; each of the circuits go to a different POP. Each of the peer > sessions receive a partial routing table from our provider. What we have > found is that load sharing (outbound to our ISP) is virtually non-existant. > > > well, i'm studying for BCSN and came across the maximum path feature, and it > seems like the solution. > > My question is this: we have enabled maximum-path 4 to load share between > the four sessions. This, however has had a neglible effect. Does the fact > that we still hear routes from the provider from different pops affect this? > > In other words, since the 4 pops are in a different geographical area, and > therefore may send a different bgp table which in turns overrides the > maximum path command. > > I want to try having the provider send a default route instead; the thought > being that our router will not have to decide on best paths, and leave that > to ISP router, but the powers to be don't want that (for some reason...) > > Does anyone have any suggestions? > thanks all, > > moe > > > > > > > _ > Get your FREE download of MSN Explorer at http://explorer.msn.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=6890&t=6887 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: BGP -Maximum Paths [7:6887]
It seems that if you are only getting partial routes from each of the connections, you are probably using your gateway of last resort for most of your outbound traffic. When you enabled the maximum-paths, you enabled load balancing for the partial routes you are getting, but again, that is probably not what most of your traffic is going to. I would then configure 4 default gateways, one for each T1. You should then load-distribute per-desiccation/per-session. Thanks -Nate "moe humm" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Hey gang, > > I have a question on maximum-paths in BGP; > > This is the scenario: 4 T1's running EBGP to our ISP in a multihome peer > session; each of the circuits go to a different POP. Each of the peer > sessions receive a partial routing table from our provider. What we have > found is that load sharing (outbound to our ISP) is virtually non-existant. > > > well, i'm studying for BCSN and came across the maximum path feature, and it > seems like the solution. > > My question is this: we have enabled maximum-path 4 to load share between > the four sessions. This, however has had a neglible effect. Does the fact > that we still hear routes from the provider from different pops affect this? > > In other words, since the 4 pops are in a different geographical area, and > therefore may send a different bgp table which in turns overrides the > maximum path command. > > I want to try having the provider send a default route instead; the thought > being that our router will not have to decide on best paths, and leave that > to ISP router, but the powers to be don't want that (for some reason...) > > Does anyone have any suggestions? > thanks all, > > moe > > > > > > > _ > Get your FREE download of MSN Explorer at http://explorer.msn.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=6907&t=6887 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: BGP -Maximum Paths [7:6887]
can you post a config Moe? would help to track down exactly what's going on thanks Andy - Original Message - From: "moe humm" To: Sent: Saturday, June 02, 2001 5:01 PM Subject: BGP -Maximum Paths [7:6887] > Hey gang, > > I have a question on maximum-paths in BGP; > > This is the scenario: 4 T1's running EBGP to our ISP in a multihome peer > session; each of the circuits go to a different POP. Each of the peer > sessions receive a partial routing table from our provider. What we have > found is that load sharing (outbound to our ISP) is virtually non-existant. > > > well, i'm studying for BCSN and came across the maximum path feature, and it > seems like the solution. > > My question is this: we have enabled maximum-path 4 to load share between > the four sessions. This, however has had a neglible effect. Does the fact > that we still hear routes from the provider from different pops affect this? > > In other words, since the 4 pops are in a different geographical area, and > therefore may send a different bgp table which in turns overrides the > maximum path command. > > I want to try having the provider send a default route instead; the thought > being that our router will not have to decide on best paths, and leave that > to ISP router, but the powers to be don't want that (for some reason...) > > Does anyone have any suggestions? > thanks all, > > moe > > > > > > > _ > Get your FREE download of MSN Explorer at http://explorer.msn.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=6912&t=6887 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]