NETGEAR FVX538v2 - ProSafe VPN Firewall Dual WAN Reference Manual page 210

ProSafe VPN Firewall 200 FVX538 Reference Manual
The IP address of the gateway WAN port can be either fixed or dynamic. If the IP address is
dynamic, a fully-qualified domain name must be used. If the IP address is fixed, a fully-qualified
domain name is optional.
VPN Road Warrior: Dual Gateway WAN Ports for Improved Reliability
In the case of the dual WAN ports on the gateway VPN firewall, the remote PC client initiates the
VPN tunnel with the active gateway WAN port (port WAN1 in this example) because the IP
address of the remote PC client is not known in advance. The gateway WAN port must act as a
responder.
Figure B-10
The IP addresses of the gateway WAN ports can be either fixed or dynamic, but a fully-qualified
domain name must always be used because the active WAN port could be either WAN1 or WAN2
(i.e., the IP address of the active WAN port is not known in advance).
B-12 Network Planning for Dual WAN Ports
v1.0, January 2010