ifconfig(8c)

Name

ifconfig − configure network interface parameters

Syntax

/etc/ifconfig interface [ address [ dest_address ] ] [ parameters ]

Description

The ifconfig command assigns an address to a network interface and/or configures network interface parameters. You must use ifconfig at boot time to define the network address of each interface present on a machine. You can also use it at a later time to redefine an interface’s address. The interface parameter is a string of the form: name, unit, for example, en0. The address is either a host name present in the host name data base, hosts(,), or a DARPA Internet address expressed in the Internet standard dot notation.

Arguments

You can set the following parameters with ifconfig:

upMarks an interface up.

downMarks an interface down. When an interface is marked down, the system does not attempt to transmit messages through that interface.

trailersEnables the use of a trailer link level encapsulation when sending. If a network interface supports trailers, the system, when possible, encapsulates outgoing messages in a manner that minimizes the number of memory-to-memory copy operations performed by the receiver. Although trailers is the default on some network interfaces, the use of trailers is not recommended; failures in trailer negotiation can disrupt network transmissions. See −trailers.

−trailersDisables the use of a trailer link level encapsulation. This is the recommended setting.

promiscEnables the use of the packetfilter() in the promiscuous mode. The promiscuous mode allows the network interface to receive all the packets off the wire and pass it onto to the packet filter.

−promiscDisables the promiscuous mode of the packet filter. This is the default.

+copyallSets the interface into copy-all mode (receives packets sent/received by the kernel-resident protocol software [for example, IP, ARP, DECnet, LAT] on this host).

−copyallDisables copy-all mode. (See pfconfig() for more information aboutut the copyall flag.)

arpEnables the use of the Address Resolution Protocol in mapping between network level addresses and link level addresses. This is the default. This is currently implemented for mapping between DARPA Internet addresses and 10Mb/s Ethernet addresses.

−arpDisables the use of the Address Resolution Protocol.

debugEnables driver-dependent debugging code. Usually, this turns on extra console error logging.

−debugDisables driver dependent debugging code.

netmaskSpecifies how many bits of the address you wish to reserve for subdividing Class A and B networks into sub-networks. (Inet only).

dstaddrSpecifies the correspondent on the other end of a point to point link.

broadcastSpecifies the address you wish to use to represent broadcasts to the network.

The ifconfig command displays the current configuration for a network interface when no optional parameters are supplied.

Only the superuser can modify the configuration of a network interface.

Diagnostics

The ifconfig command returns messages indicating the specified interface does not exist, the requested address is unknown, the user tried to alter an interface’s configuration but is not privileged.

Museum