ifconfig(1M) MISC. REFERENCE MANUAL PAGES ifconfig(1M)
NAME
ifconfig - configure network interface parameters
SYNOPSIS
ifconfig interface [ address_family ] [ address [
dest_address ] ] [ parameters ]
[ netmask mask ] [ broadcast address ] [ metric
n ]
ifconfig interface [ protocol_family ]
DESCRIPTION
ifconfig is used to assign an address to a network interface
and/or to configure network interface parameters. ifconfig
must be used at boot time to define the network address of
each interface present on a machine; it may also be used at
a later time to redefine an interface's address or other
operating parameters. Used without options, ifconfig
displays the current configuration for a network interface.
If a protocol family is specified, ifconfig will report only
the details specific to that protocol family. Only the
super-user may modify the configuration of a network inter-
face.
The interface parameter is a string of the form name unit,
for example en0. The interface name -a is reserved, and
causes the remainder of the arguments to be applied to each
address of each interface in turn.
Since an interface may receive transmissions in differing
protocols, each of which may require separate naming
schemes, the parameters and addresses are interpreted
according to the rules of some address family, specified by
the address_family parameter. The address families
currently supported are ether and inet. If no address fam-
ily is specified, inet is assumed.
For the DARPA Internet family (inet), the address is either
a host name present in the host name data base [see
hosts(4)], or a DARPA Internet address expressed in the
Internet standard dot notation. Typically, an Internet
address specified in dot notation will consist of your
system's network number and the machine's unique host
number. A typical Internet address is 192.9.200.44, where
192.9.200 is the network number and 44 is the machine's host
number.
For the ether address family, the address is an Ethernet
address represented as x:x:x:x:x:x where x is a hexadecimal
number between 0 and ff. Only the super-user may use the
ether address family.
Last change: TCP/IP 1
ifconfig(1M) MISC. REFERENCE MANUAL PAGES ifconfig(1M)
If the dest_address parameter is supplied in addition to the
address parameter, it specifies the address of the
correspondent on the other end of a point to point link.
OPTIONS
The following parameters may be set with ifconfig:
up Mark an interface up. This may be used to enable an
interface after an ifconfig down. It happens
automatically when setting the first address on an
interface. If the interface was reset when previ-
ously marked down, the hardware will be re-
initialized.
down Mark an interface down. When an interface is marked
down, the system will not attempt to transmit mes-
sages through that interface. If possible, the
interface will be reset to disable reception as well.
This action does not automatically disable routes
using the interface.
trailers
(inet only) Enable the use of a trailer link level
encapsulation when sending. If a network interface
supports trailer encapsulation, the system will, when
possible, encapsulate outgoing messages in a manner
which minimizes the number of memory to memory copy
operations performed by the receiver. This feature
is machine-dependent, and therefore not recommended.
On networks that support the Address Resolution Pro-
tocol [see arp(7)]; currently, only 10 Mb/s Ether-
net), this flag indicates that the system should
request that other systems use trailer encapsulation
when sending to this host. Similarly, trailer encap-
sulations will be used when sending to other hosts
that have made such requests.
-trailers
Disable the use of a trailer link level encapsula-
tion.
arp Enable the use of the Address Resolution Protocol in
mapping between network level addresses and link
level addresses (default). This is currently imple-
mented for mapping between DARPA Internet addresses
and 10Mb/s Ethernet addresses.
-arp Disable the use of the Address Resolution Protocol.
metric n
Set the routing metric of the interface to n, default
0. The routing metric is used by the routing
Last change: TCP/IP 2
ifconfig(1M) MISC. REFERENCE MANUAL PAGES ifconfig(1M)
protocol [routed(1M)]. Higher metrics have the
effect of making a route less favorable; metrics are
counted as addition hops to the destination network
or host.
netmask mask
(inet only) Specify how much of the address to
reserve for subdividing networks into sub-networks.
The mask includes the network part of the local
address and the subnet part, which is taken from the
host field of the address. The mask can be specified
as a single hexadecimal number with a leading 0x,
with a dot-notation Internet address, or with a
pseudo-network name listed in the network table net-
works(4). The mask contains 1's for the bit posi-
tions in the 32-bit address which are to be used for
the network and subnet parts, and 0's for the host
part. The mask should contain at least the standard
network portion, and the subnet field should be con-
tiguous with the network portion. If a + (plus sign)
is given for the netmask value, then the network
number is looked up in the /etc/netmasks file.
broadcast address
(inet only) Specify the address to use to represent
broadcasts to the network. The default broadcast
address is the address with a host part of all 0's.
A + (plus sign) given for the broadcast value causes
the broadcast address to be reset to a default
appropriate for the (possibly new) Internet address
and netmask. Note that the arguments of ifconfig are
interpreted left to right, and therefore
ifconfig -a netmask + broadcast +
and
ifconfig -a broadcast + netmask +
may result in different values being assigned for the
interfaces' broadcast addresses.
EXAMPLES
If your workstation is not attached to an Ethernet, the en0
interface should be marked down as follows:
ifconfig en0 down
To print out the addressing information for each interface,
use
ifconfig -a
Last change: TCP/IP 3
ifconfig(1M) MISC. REFERENCE MANUAL PAGES ifconfig(1M)
To reset each interface's broadcast address after the net-
masks have been correctly set, use
ifconfig -a broadcast +
FILES
/dev/nit
/etc/netmasks
SEE ALSO
netstat(1M), netmasks(4).
DIAGNOSTICS
Messages indicating the specified interface does not exist,
the requested address is unknown, or the user is not
privileged and tried to alter an interface's configuration.
Last change: TCP/IP 4