I tried this for the first time today....... but couldn't get too far
Turns out, I can't enter the IP address of a router which is outside of my local subnet.
Is this by design or is it a bug?
If it's by design, then it limits the usefulness of the tool as I would expect many people have routers that are not on their local subnet - other end of a WAN link for example.
In my case, it is the other side of my firewall, switching from a private to a public address range.
