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New Member

adsl as fault tolerant link?

I have a triangle of dedicated T-1's running between 3 locations, Los Angeles, San Francisco and Las Vegas.

The recent rains in Northern California flooded out one of the manholes my SF T-1 goes through and our link to SF was down for a week. I have 3 2620's running a version 12.0 IOS with two T-1 WIC cards in each. (It's a triangle, so each end point has two links). All of this is private, no internet connection. My bosses are now interested in some kind of additional fault tolerance. Because of line useage, it looks like a 384k link would be acceptable for the Los Angeles to SF link. With the 2620's is it possible to bring in a DSL link to each location, put an adsl WIC card such as the WIC-1ADSL in each 2620 and have the 2620's do a VPN between each location and something like CEF so that the DSL line is a fault tolerant link, NOT an internet link? My guess is there are 3 parts to that question. 1. can I configure 2 VPN connections at each 2620 at all?

2. Will the VPN software kill the 2620's processor?

3. Can CEF be configured between the T-1 and the DSL link?


Re: adsl as fault tolerant link?



A1) yes two VPN tunnels are possible with proper IOS

A2) not likely given less than 2 Mbps throughput. In your case the additional DSL will be used for backup purposes, so only little additional CPU load from it.

A3) CEF can be used in this scenario. I am not sure what you mean by "between".

Remark: make sure routing wise the two T1 are not better than your DSL backup.

Did it help? Then please rate it.


New Member

Re: adsl as fault tolerant link?

Thanks, I had two ideas mixed together in my head. One of the ideas was combining the DSL's throughput capacity with the existing T-1 so that when they both work I am getting additional bandwidth, and 2 if either the DSL link or the T-1 goes down, the other line handles the load.

I was watching the load on the 3 links, LA- Las Vegas is running 300kbp/s to 500kbps with spikes to 1.5mbp/s, LA-SF is 100kbps to 200kbps with spikes to 500kbps, LA-San Diego is 200kbps to 400kbps with spikes to 800kbps. And finally the SF-Las Vegas link was running at 2kbps with spikes to 16kbps.