Verifying the configuration of network interfaces

The ifconfig(1Mtcp) command displays information about the configuration for a named network interface. To find out the configuration for all network devices that are currently installed, enter:

ifconfig -a

This command will display output similar to the following. The exact format will depend on the network interfaces that are configured on your system.

net0: flags=4043<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
        inet 150.162.7.7 netmask ffffff00 broadcast 150.162.7.255
        perf. params: recv size: 4096; send size: 8192; full-size frames: 1
        ether 00:20:af:f2:91:19
        (alias) inet 150.162.7.52 netmask ffffff00 broadcast 150.162.7.255
        (alias) inet 150.162.7.54 netmask ffffff00 broadcast 150.162.7.255
lo0: flags=4049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 8232
        inet 127.0.0.1 netmask ff000000
        perf. params: recv size: 4096; send size: 8192; full-size frames: 1
        (alias) inet 127.0.0.1 netmask ff000000

• The ``flags'' field indicates that the interface is up, that it allows broadcasts, that the interface is running with no problems, and that it is configured to be able to use multicasting.

• The maximum transmission unit (``mtu'') for the network is 1500 bytes.

• The line beginning ``inet'' displays the Internet address of this interface, the netmask, and the network broadcast address.

• The performance parameters that are configured for the interface. In this example, the TCP receive and send window sizes are set to 4096 and 8192 bytes. The value 1 for ``full-size frames'' indicates that TCP will use all available space in a frame for a segment.

• The line beginning ``ether'' shows that this is an Ethernet network adapter with its associated MAC address.

• The second ``alias'' entry shows that this interface has two IP addresses.

The lo0 entry is for the loopback interface. This is used for communication using the Internet protocols on the host itself.