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ProSafe Dual WAN Gigabit Firewall with SSL & IPsec VPN FVS336G Reference Manual
C-10
Network Planning for Dual WAN Ports
v1.0, October 2007
Virtual Private Networks (VPNs)
When implementing virtual private network (VPN) tunnels, a mechanism must be used for 
determining the IP addresses of the tunnel end points. The addressing of the firewall’s dual WAN 
port depends on the configuration being implemented:
For the single gateway WAN port case, the mechanism is to use a fully-qualified domain name 
(FQDN) when the IP address is dynamic and to use either an FQDN or the IP address itself when 
the IP address is fixed. The situation is different when dual gateway WAN ports are used in a 
rollover-based system.
Rollover Case for Dual Gateway WAN Ports
Rollover (
) for the dual gateway WAN port case is different from the single 
gateway WAN port case when specifying the IP address of the VPN tunnel end point. Only 
one WAN port is active at a time and when it rolls over, the IP address of the active WAN port 
always changes. Hence, the use of a fully-qualified domain name is always required, even 
when the IP address of each WAN port is fixed.
Table C-2.  IP addressing requirements for VPNs in dual WAN port systems
Configuration and WAN IP address
Single WAN Port
(reference case)
Dual WAN Port Cases
Rollover
a
a. All tunnels must be re-established after a rollover using the new WAN IP address.
Load Balancing
VPN Road Warrior
(client-to-gateway)
Fixed
Allowed
(FQDN optional)
FQDN required
Allowed
(FQDN optional)
Dynamic
FQDN required
FQDN required
FQDN required
VPN Gateway-to-Gateway Fixed
Allowed
(FQDN optional)
FQDN required
Allowed
(FQDN optional)
Dynamic
FQDN required
FQDN required
FQDN required
VPN Telecommuter
(client-to-gateway through 
a NAT router)
Fixed
Allowed
(FQDN optional)
FQDN required
Allowed
(FQDN optional)
Dynamic
FQDN required
FQDN required
FQDN required
Note: Once the gateway router WAN port rolls over, the VPN tunnel collapses and must 
be re-established using the new WAN IP address.