Specifications

Chapter 4. Configuring Special Features 77
Multiple IP Subnets
You may configure the router to provide access to multiple IP subnets on the Ethernet network. (This feature does
not apply to IPX or bridged traffic.)
Each IP subnet is referenced as a logical (or virtual) Ethernet interface. You may define multiple logical interfaces
for each physical Ethernet interface (that is, port) in the router. Each logical interface is referenced by its port
number and logical interface number (port #:logical#).
Logical Interface Commands
To define a logical interface, first use the eth add command (page 229); it specifies the port number and the new
logical interface number. You then enter an eth ip addr command (page 231) to define the IP address and subnet
mask of the IP subnet.
The default logical interface for each port is interface 0; this logical interface 0 always exists and cannot be
deleted. (Other logical interfaces may be deleted using the eth delete command [page 230].)
Stopping and Starting an Interface
You can stop and start a logical interface without rebooting the entire router. To do so, use these commands:
¥ eth ip stop Stops a logical Ethernet interface (page 245).
¥ eth ip start Starts a logical Ethernet interface (page 244).
¥ eth ip restart Stops and restarts a logical Ethernet interface (page 244).
Note: When you stop or restart an interface, interface changes are discarded if they have not been saved.
Interface Routing and Filtering
After the eth add and eth ip addr commands define the Ethernet logical interface, other eth commands can
reference it, including:
¥ eth ip addRoute Adds an Ethernet IP route that uses the logical Ethernet interface. The route is added to
the default routing table (page 231).
¥ eth ip bindRoute Adds an Ethernet IP route that uses the logical Ethernet interface. The route is added to a
virtual routing table (page 233).
¥ eth ip filter Manages IP filters for the logical Ethernet interface. Lists of input, output, and forward
filters may be defined for the interface (page 237).
¥ eth ip options Sets RIP options for the logical interface; these options set IP routing information
protocol controls (page 243).
Note: In general, logical interface commands are not effective until you save the change and either restart the
logical interface or reboot the router. However, the eth ip bindRoute and eth ip filter commands are effective
immediately if the logical Ethernet interface is already active.