Need help setting up the WarRoom and the persistence for a server i'm maintaining
Yes the external IP should be the one you connect to the server with. If they use Windows servers they might need to 'unblock' the alive.cfg file as Windows Server 2008 or greater will try and protect you by blocking access to it. Try opening a support ticket with the provider and explain what you are trying to do. Copy/paste the WR setup instructions into the support ticket for their information.
IPs work a bit odd with these gameserver providers. Typically the machine has 2 IPs, 1 that lets players connect to the server and another that's used for outbound traffic. The "real" IP that the War Room sees should be reported somewhere in the server RPT (search for the string
YOUR SERVER EXTERNAL IP ADDRESS AS SEEN BY WAR ROOM).
I'm assuming you're paying for this, correct? My experience is (I don't host but know people that do), this comes with the expectation their customer service reps will help you.
Pass along the instructions and ask them to help you get this thing going. This is what you pay for.