ifconfig - configure network interface parameters
/usr/etc/ifconfig interface [ address_family ]
[ address [ dest_address ] ] [ netmask mask ]
[ broadcast address ] [ up ] [ down ] [ trailers ]
[ -trailers ] [ arp ] [ -arp ] [ private ]
[ -private ] [ metric n ] [ auto-revarp ]
/usr/etc/ifconfig interface [ protocol_family ]
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 pro-
tocol family is specified, ifconfig will report only the details spe-
cific to that protocol family. Only the super-user may modify the con-
figuration of a network interface.
The interface parameter is a string of the form nameunit, for example
le0 or ie1. Three special interface names, -a, -ad and -au, are
reserved and refer to all or a subset of the interfaces in the system.
If one of these interface names is given, the commands following it are
applied to all of the interfaces that match:
-a Apply the commands to all interfaces in the system.
-ad Apply the commands to all ``down'' interfaces in the
-au Apply the commands to all ``up'' interfaces in the sys-
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 fam-
ily, specified by the address_family parameter. The address families
currently supported are ether and inet. If no address family is speci-
fied, inet is assumed.
For the TCP/IP family (inet), the address is either a host name present
in the host name data base (see hosts(5)) or in the Network Information
Service (NIS) map hosts, or a TCP/IP 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
22.214.171.124, 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 repre-
sented 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.
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.
up Mark an interface "up". This happens automatically when
setting the first address on an interface. The up
option enables an interface after an ifconfig down,
reinitializing the hardware.
down Mark an interface "down". When an interface is marked
"down", the system will not attempt to transmit messages
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 This flag used to cause a non-standard encapsulation of
inet packets on certain link levels. Sun drivers no
longer use this flag, but it is ignored for compatibil-
-trailers Disable the use of a "trailer" link level encapsulation.
arp Enable the use of the Address Resolution Protocol in
mapping between network level addresses and link level
addresses (default). This is currently implemented for
mapping between TCP/IP addresses and 10Mb/s Ethernet
-arp Disable the use of the Address Resolution Protocol.
private Tells the in.routed routing daemon (see routed(8C)) that
the interface should not be advertised.
-private Specify unadvertised interfaces.
auto-revarp Use the Reverse Address Resolution Protocol (RARP) to
automatically acquire an address for this interface.
Available beginning with SunOS 4.1.1 Rev B.
metric n Set the routing metric of the interface to n, default 0.
The routing metric is used by the routing protocol
(routed(8C)). 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 hexadec-
imal number with a leading 0x, with a dot-notation
address, or with a pseudo-network name listed in the
network table networks(5). The mask contains 1's for
the bit positions 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 stan-
dard network portion, and the subnet field should be
contiguous with the network portion. If a `+' (plus
sign) is given for the netmask value, then the network
number is looked up in the NIS netmasks.byaddr map (or
in the /etc/netmasks) file if not running the NIS ser-
(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) address and netmask. Note that
the arguments of ifconfig are interpreted left to right,
ifconfig -a netmask + broadcast +
ifconfig -a broadcast + netmask +
may result in different values being assigned for the
interfaces' broadcast addresses.
If your workstation is not attached to an Ethernet, the ie0 interface
should be marked "down" as follows:
ifconfig ie0 down
To print out the addressing information for each interface, use
To reset each interface's broadcast address after the netmasks have
been correctly set, use
ifconfig -a broadcast +
intro(3), ethers(3N), arp(4P), hosts(5), netmasks(5), networks(5) net-
stat(8C), rc(8), routed(8C)
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.
The network information service (NIS) was formerly known as Sun Yellow
Pages (YP). The functionality of the two remains the same; only the
name has changed.
14 December 1990 IFCONFIG(8C)