User guide

76 Chapter 4. Configuring Special Features
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 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#).
To define a logical interface to route traffic for an IP subnet, first use the eth add command (page 167); it
specifies the port number and the new logical interface number. You then enter an eth ip addr command (page
168) 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 168].)
After the eth add and eth ip addr commands define the Ethernet logical interface, the logical interface can be
referenced by other eth commands, 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 169).
¥ eth ip bindRoute Adds an Ethernet IP route that uses the logical Ethernet interface. The route is added to a
virtual routing table (page 169).
¥ 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 172).
¥ eth ip options Sets RIP options for the logical interface; these options set IP routing information
protocol controls (page 178).
Note: In general, these commands are not effective until you enter save and reboot. However, the eth ip
bindRoute and eth ip filter commands will take effect before a save and reboot if the logical Ethernet interface
is already active.