Threshold on a DS-3 running BGP

[kcchief01]

Quick question....

I have a scenario where I have a primary DS-3 with a Shadow DS-3 as the backup. The Shadow DS-3 is only to be used in the event the primary fails, so we are manually setting the MED to poison the path through the Shadow DS-3. This works fine as a backup solution, but it is now requested that the Shadow DS-3 be active in the event that the primary hits a certain bandwidth usage. Kind of like setting the threshold on an ISDN line, but I don't think that this is possible. I've search CCO, but I haven't had much luck. I spoke with the ISP and they don't think it is possible either.

I am just wanting to verify my thinking on this before I go to the people wanting this functionality and tell them that it is not possible.

Thanks!

Eric

[mmikhail]

I believe there's no way to achieve that through BGP.

However You can do it locally between your site and your ISP: either using backup threshold (if both links terminate at same router both ends), or by using and tweaking some IGP that use load metric and variance in the routing decision (EIGRP?) between you and the ISP (underneath your BGP).

How about load balancing?

[kcchief01]

The only problem is that these links go to different locations, and I'm not sure if UUNET will be want to configure EIGRP on these links. They don't want to do any load balancing because they don't want traffic to flow across the Shadow DS-3 unless there is an outage, or in the event that the primary DS-3 becomes saturated.

I think I will just have to let them know it can't be accomplished while maintaining their original requirements. The cost of the Shadow DS-3 is based on how much traffic goes across it. Hence, they don't want to use it unless they have to.

I appreciate your comments and if you can think of another way to accomplish this post it on the board!

Thanks!

Eric