Best way to detect Internet outage?

One of my customers has a business class cable Internet connection with Comcast. Over the past few weeks we started having outages with them and they're still monitoring things on their end. I'm trying to figure out if there's some way I can determine when the line is going down and for how long by looking at the logs on the Astaro. The only thing we know at this point is that it's something outside the building, and not related to the equipment inside the building. So I figure the more information I can provide the better. As of right now I'm only notified when the phones drop, which isn't the most accurate.

We're currently on 8.308. I found an option called Uplink Monitoring, but I have no idea how it works, since there's really no information in the help menu. It doesn't say what "automatic monitoring" checks for, nor how often it pings an address...and if that's configurable. Since it's an issue with the outside line, the interface itself is not going down and it's still able to ping the Comcast gateway...so we really need to be pinging an outside IP address.

Another idea I had was checking the VPN logs since this particular site is the endpoint for 2 IPSec VPN tunnels. I figured if I check the log I can see when the tunnel is going down and when it comes back up, unfortunately I don't look through these logs often and it's hard for me to tell what's normal communication. Is there a specific line I should look for where I can see that the tunnel dropped and/or where it's re-establishing communication after a link failure?

Thanks, guys.