Quick Reference Guide

ProSafe VPN Firewall 50 FVS338 Reference Manual
3-2 LAN Configuration
v1.0, January 2010
The VPN firewall will deliver the following parameters to any LAN device that requests DHCP:
• An IP address from the range that you have defined.
• Subnet mask.
• Gateway IP address (the VPN firewall’s LAN IP address).
• Primary DNS server (the VPN firewall’s LAN IP address).
• WINS server (if you entered a WINS server address in the DHCP section of the LAN Setup
screen).
• Lease time (date obtained and duration of lease).
DHCP Relay options allow you to make the VPN firewall a DHCP relay agent. The DHCP relay
agent makes it possible for DHCP broadcast messages to be sent over routers that do not support
forwarding of these types of messages. The DHCP Relay Agent is therefore the routing protocol
that enables DHCP clients to obtain IP addresses from a DHCP server on a remote subnet, or
which is not located on the local subnet. If you have no configured DHCP relay agent, your clients
would only be able to obtain IP addresses from the DHCP server which is on the same subnet. To
enable clients to obtain IP addresses from a DHCP server on a remote subnet, you have to
configure the DHCP relay agent on the subnet that contains the remote clients, so that it can relay
DHCP broadcast messages to your DHCP server.
When the DNS Proxy option is enabled, the VPN firewall will act as a proxy for all DNS requests
and communicate with the ISP’s DNS servers (as configured on the Broadband ISP Settings screen
and Dial-up ISP Settings screen). All DHCP clients will receive the primary/secondary DNS IP
addresses along with the IP address where the DNS proxy is running, which is the the devices’s
LAN IP address. When disabled, all DHCP clients will receive the DNS IP addresses of the ISP
excluding the DNS proxy IP address. The feature is particularly useful in Auto Rollover mode. For
example, if the DNS servers for each connection are different, then a link failure may render the
DNS servers inaccessible. However, when the DNS proxy is enabled, then clients can make
requests to the VPN firewall and the VPN firewall, in turn, sends those requests to the DNS servers
of the active connection.
Configuring the LAN Setup Options
The LAN Setup screen allows configuration of LAN IP services such as DHCP and allows you to
configure a secondary or “multi-home” LAN IP setup in the LAN. The default values are suitable
for most users and situations. Disable the DNS Proxy if you are using a dual WAN configuration
with route diversity and failover. These are advanced settings most usually configured by a
network administrator.