Using Local Ip Address With An Unbound Network - D-Link NetDefendOS User Manual

ARP queries. ARP works because the clients and the NetDefendOS interface are part of the same
network.
A second network might then be added to the same physical interface via a switch, but with a
new network range that does not include the physical interface's IP address. This network is said
to be not bound to the physical interface. Clients on this second network will not then be able to
communicate with the NetDefend Firewall because ARP will not function between the clients
and the interface.
To solve this problem, a new route is added to NetDefendOS with the following parameters:
• Interface: The interface on which the second network is found.
• Network: The IP address range of the second network.
• Local IP Address: An address within the second network's IP range.
When the Default Gateway of the second network's clients is now set to the same value as the
Local IP Address of the above route, the clients will be able to communicate successfully with the
interface. The IP address chosen in the second network is not significant, as long as it is the same
value for the Default Gateway of the clients and the Local IP Address.
The effect of adding the route with the Local IP Address is that the firewall will act as a gateway
with the Local IP Address and respond to, as well as send out, ARP queries as though the interface
had that IP address.
The diagram below illustrates a scenario where this feature could be used. The network
10.1.1.0/24 is bound to a physical interface that has an IP address within the network of 10.1.1.1. If
we now attach a second network 10.2.2.0/24 to the interface via the switch, it is unbound since
the interface's IP address does not belong to it.
Figure 4.2. Using Local IP Address with an Unbound Network
By adding a NetDefendOS route for this second network with the Local IP Address specified as
10.2.2.1, the interface will then respond to ARP requests from the 10.2.2.0/24 network. The clients
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Chapter 4: Routing