ifconfig(8c)
NAME
ifconfig − configure network interface parameters
SYNTAX
/etc/ifconfig interface address_family [ address [ dest_address ] ] [ parameters ]
/etc/ifconfig interface [ protocol_family ]
DESCRIPTION
The ifconfig program is used to assign an address to a network interface and/or configure network interface parameters. The ifconfig program must be used at boot time to define the network address of each interface present on a machine. It also may be used at a later time to redefine an interface’s address. The interface parameter is a string of the form “name unit”, for example, “en0”.
Because an interface may receive transmissions in differing protocols (each of which may required separate naming schemes), it is necessary to specify the protocol_family, which may change the interpretation of the remaining parameters. The address protocols current supported are “inet” and “ns”.
For the DARPA-Internet family, the address is either a name present in the host name data base, hosts(5), or a DARPA Internet address expressed in the Internet standard “dot notation”. For the Xerox Network Systems(tm) family, addresses are net:a.b.c.d.e.f, where net is the assigned network number (in decimal), and each of the next six bytes are specified in hexadecimal.
The following parameters may be set with ifconfig:
up Mark an interface “up”.
down Mark an interface “down”. When an interface is marked “down”, the system will not attempt to transmit messages through that interface.
trailers Enable the use of a “trailer” link level encapsulation when sending (default). If a network interface supports trailers, 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.
-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 DARPA Internet addresses and 10Mb/s Ethernet addresses.
-arp Disable the use of the Address Resolution Protocol.
debug Enable driver dependent debugging code; usually, this turns on extra console error logging.
-debug Disable driver dependent debugging code.
netmask Specify how much of the address you wish to reserve for subdiving Class A and B networks into sub-networks (inet only).
dstaddr Specify the correspondent on the other end of a point-to-point link.
broadcast Specify the address you wish to use to represent broadcasts to the network.
The ifconfig program displays the current configuration for a network interface when no optional parameters are supplied. If a protocol family is specified, ifconfig will report only the details specific to that protocol family.
Only the superuser may modify the configuration of a network interface.
DIAGNOSTICS
Messages indicating the specified interface does not exit, the requested address is unknown, the user is not privileged and tried to alter an interface’s configuration.