Configuring Ethernet Subinterfaces - Lucent Technologies PortMaster 4 Configuration Manual

Table of Contents

Configuring Ethernet Subinterfaces

With the subinterface feature of ComOS, you can create up to 512 subinterfaces (the

total number of interfaces available on a PortMaster) on the Ether0 interface on the

PortMaster 4. Because you have the bandwidth of only a single Ethernet interface,

however, efficiency begins to degrade significantly when you add more than eight

subinterfaces.

Note – The PortMaster 4 supports Ethernet subinterfaces only on Ether0.

Subinterfacing is essentially the segmenting of a single wire, or port, into multiple IP

networks. Instead of subnetting and routing, you can create a subinterface and then set

it up as you would a standard Ethernet interface. To avoid routing loops, however, you

must be sure not to create two subinterfaces in the same TCP/IP network on the same

port. Each Ethernet subinterface must have a unique network.

A drawback to subinterfacing is that it supports static routing only; IPX, RIP, OSPF,

packet filtering, and route propagation are not supported on subinterfaces.

You must configure the primary Ethernet interface before adding subinterfaces. (See

"Setting General Ethernet Parameters" on page 4-3 for details.) After you configure the

primary Ethernet interface, follow this procedure to add a subinterface.

1. Create a subinterface.

Command> add subinterface Name

This command adds an entry to the subinterface table, which you can then view

with the show table subinterface command. Remove a subinterface from the

subinterface table with the delete subinterface command.

2. Associate the subinterface with a physical port.

Command> set subinterface Name port Portlabel

3. Assign an IP address or an IP address and netmask to the subinterface.

Command> set subinterface Name Ipaddress [/NM]|[Ipaddress/NM]

You can specify the netmask in the /NM or dotted decimal format. You can also

configure the IP address and netmask separately (see the PortMaster 4 Command Line

Reference for details).

4. Set the broadcast for the interface.

Command> set subinterface Name broadcast high|low

5. Save the setting to nonvolatile RAM, and reset the interface.

Command> save all

Command> reset slot10

Because Ethernet subinterfaces are rebuilt every time a new subinterface is added, you

can view but not modify an Ethernet subinterface using the ifconfig command (see the

PortMaster 4 Command Line Reference).

Configuring an Ethernet Interface