NETGEAR UTM5-100NAS, UTM50-100NAS manual Dhcp Relay, DNS Proxy

ProSecure Unified Threat Management (UTM) Appliance Reference Manual

The UTM delivers the following settings to any LAN device that requests DHCP:

•An IP address from the range that you have defined

•Subnet mask

•Gateway IP address (the UTM’s LAN IP address)

•Primary DNS server (the UTM’s LAN IP address)

•WINS server (if you entered a WINS server address in the DHCP Setup menu)

•Lease time (the date obtained and the duration of the lease).

DHCP Relay

DHCP relay options allow you to make the UTM a DHCP relay agent for a VLAN. 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. If you do not configure a DHCP Relay Agent for a VLAN, its clients can only obtain IP addresses from a DHCP server that is on the same subnet. To enable clients to obtain IP addresses from a DHCP server on a remote subnet, you must configure the DHCP Relay Agent on the subnet that contains the remote clients, so that the DHCP Relay Agent can relay DHCP broadcast messages to your DHCP server.

DNS Proxy

When the DNS Proxy option is enabled for a VLAN, the UTM acts as a proxy for all DNS requests and communicates with the ISP’s DNS servers (as configured on the WAN ISP Settings screens). All DHCP clients receive the primary and secondary DNS IP addresses along with the IP address where the DNS proxy is located (that is, the UTM's LAN IP address). When the DNS Proxy option is disabled for a VLAN, all DHCP clients receive the DNS IP addresses of the ISP but without the DNS proxy IP address. A DNS proxy is particularly useful in auto-rollover mode. For example, if the DNS servers for each WAN connection are different servers, then a link failure might render the DNS servers inaccessible. However, when the DNS Proxy option is enabled, the DHCP clients can make requests to the UTM, which, in turn, can send those requests to the DNS servers of the active WAN connection. However, disable the DNS Proxy if you are using a dual-WAN configuration in auto-rollover mode with route diversity (that is, with two different ISPs) and you cannot ensure that the DNS server is available after a rollover has occurred.

LAN Configuration 4-5

v1.0, January 2010