What are the typical reasons for these not to work? From the user guide it appears to use IPSEC, so I assume anything that prevents a VPN?
Verizon support told the customer they needed a Class A address. WTF? Did they maybe mean it can't be a class A address? Customer uses 10.x.x.x addresses internally, behind Cisco ASA firewall (which I don't manage). I do see some udp/500 and udp/4500 packets, I think that means something is using UDP for IPSEC NAT traversal?
