Using Local Ip Address With An Unbound Network - D-Link DFL-1660 User Manual

4.2.1. The Principles of Routing
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 won't then be able to
communicate with the NetDefend Firewall because ARP won't 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 NetDefendOS 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
in this second network must also have their Default Gateway set to 10.2.2.1 in order to reach the
NetDefend Firewall.
171
Chapter 4. Routing