IFCONFIG(8)

NAME
ifconfig - configure a network interface

SYNOPSIS
ifconfig [interface]
ifconfig interface options | address ...

DESCRIPTION
Ifconfig is used to set up (and maintain thereafter) the kernel-resident network interfaces. It is used at boot time to configure most of them to a running state. After that, it is usually only needed when debugging or when system tuning is needed.

If no arguments are given, ifconfig just displays the status of the currently defined interfaces. If the single interface argument is given, it displays the status of the given interface only. Otherwise, it assumes that things have to be set up.

OPTIONS

interface
    The name of the NET interface. This usually is a name like wd0 , sl3 or something like that: a device driver name followed by a unit number.

up  This flag causes the interface to be activated. It is implicitly specified if the interface is given a new address (see below).

down
    This flag causes the driver for this interface to be shut down, and is useful when things start going wrong.

metric N
    This parameter sets the interface metric. It is not used at present, but we implement it for the future.

mtu N
    This parameter sets the Maximum Transfer Unit (MTU) of an interface. For Ethernet, this is a number in the range of 1000-2000 (default is 1500). For SLIP, use something between 200 and 4096. Note, that the current implementation does not handle IP fragmentation yet, so you'd better make the MTU large enough!

[-]arp
    Enable or disable the use of the ARP protocol on this interface. If the minus (-)sign is present, the flag is turned OFF.

[-]trailers
    Enable or disable the use of trailers on Ethernet frames. This is not used in the current implementation of NET.

broadcast aa.bb.cc.dd
    Set the IP broadcast address for this interface. This defaults to the standard 255.255.255.255 address, but it can be set to any value. Certain old BSD UNIX systems still use the 0.0.0.0 address, for example.

dstaddr aa.bb.cc.dd
    Set the "other end"'s IP address in case of a Point-To-Point link, like PPP. Not used at present.

netmask aa.bb.cc.dd
    Set the IP network mask for this interface. This value defaults to the usual class A, B or C network mask (as deducted from the interface IP address), but it can be set to any value for the use of subnetting.

address
    The host name or IP address (a host name will be resolved into an IP address) of that interface. This parameter is required, although the syntax doesn't currently require it.

FILES
/proc/net/dev , /dev/inet

BUGS
None so far, although the syntax checking could be better.

AUTHOR
Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>