[c-nsp] Peering + transit backup between 2 ISPs

[Stephen J. Wilcox]

On Thu, 24 Nov 2005, Vincent De Keyzer wrote:

> Hello,
> 
>  
> 
> let ISP A and ISP B, which both have routers in a given room. They are good
> friends and they would like to achieve the following:
> 
> 1.	set-up a peering to exchange own AS routes
> 2.	serve as backup transit one for the other: each ISP would have one
> upstream only, and when the unique upstream goes down, it would then (and
> only then) use the other ISP for transit 
> 
> Is this feasible? I can't really figure out how this could be achieved
> without having both ISPs offering transit to each other all of the time.

in my limited observations of these arrangements they are notorious for causing 
problems.

make sure you implement as many failsafes and as little trust as you are able to 
in your configs

on balance, for the general situation i'm not convinced the benefits outweigh 
the drawbacks.. one question to consider is for your backup partner, would you 
buy ordinary transit from them? if the answer is no then trusting them to handle 
this is not much different

Steve