IFCONFIG
Section: (8)
Updated: 06 October 1993
Index
Return to Main Contents
NAME
ifconfig - configure a network interface
SYNOPSIS
ifconfig [interface]
ifconfig interface [aftype] 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.
Address Families
If the first argument after the interface name is recognized as
the name of a supported address family, that address family is
used for decoding and displaying all protocol addresses. Currently
supported address families include
inet
(TCP/IP, default) and
ax25
(AMPR Packet Radio.)
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.
- [-]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.
- [-]allmulti
-
Enable or disable the
promiscuous
mode of the interface. This means that all incoming frames get sent to
the network layer of the system kernel, allowing for networking monitoring.
- 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!
- dstaddr addr
-
Set the "other end"'s IP address in case of a Point-To-Point link, like
PPP. This keywords is obsoleted by the new
pointopoint
keyword.
- netmask addr
-
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.
- [-]broadcast [addr]
-
If the address argument is also given, set the protocol broadcast
address for this interface. Otherwise, it only sets the
IFF_BROADCAST
flag of the interface. If the keyword was preceded by a minus
(-)
sign, then the flag is cleared instead.
- [-]pointopoint [addr]
-
This keyword enables the
point-to-point
mode of an interface, meaning that it is a direct link between two
machines with nobody else listening on it (or, at least we hope that
this is the case, grin :-)
If the address argument is also given, set the protocol address of
the other side of the link, just like the obsolete
dstaddr
keyword does. Otherwise, it only sets the
IFF_POINTOPOINT
flag of the interface. If the keyword was preceded by a minus
(-)
sign, then the flag is cleared instead.
- hw
-
Set the hardware address of this interface, if the device driver
supports this operation. The keyword must be followed by the
name of the hardware class and the printable ASCII equivalent of
the hardware address. Hardware classes currently supported include
ether
(Ethernet),
ax25
(AMPR AX.25), and
ARCnet
- 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/socket /proc/net/dev
BUGS
None so far, although the syntax checking could be better.
AUTHOR
Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- Address Families
-
- OPTIONS
-
- FILES
-
- BUGS
-
- AUTHOR
-
This document was created by
man2html,
using the manual pages.
Time: 00:43:31 GMT, May 19, 2025