I am subscribed to two ISPs, a fast expensive one and a cheap but slower one. They use different technologies, cable and ADSL, so there isn't much of a single point of failure, and all my comms equipment is powered from a UPS.
ISPs in the UK go down in a fairly random pattern. Over many years I've yet to encounter a moment when both my ISPs have gone down simultaneously, so clearly the two-ISP strategy is helpful if you want uninterrupted net access here.
The problem however is how to organize your site's networking to take advantage of this improved availability. Many ISPs don't allow you to run your own AS and routing protocols, so you're mostly stuck with splitting your static routing across your two egress pipes by destination. This is less than brilliant, and requires manual intervention when one ISP drops off the face of the planet. With the help of numerous scripts I handle ISP outages with reasonable success and not much effort, and it's become business as usual. It's not great though. It feels like some technology is missing.
- Is there a better way, generally?
- Is there a better way for IPv6 only (I have dual stack on one ISP, and could tunnel on the other)? That would be a clear boon for IPv6.