ifconfig(1M)

NAME | SYNOPSIS | DESCRIPTION | ATTRIBUTES | NOTES | DIAGNOSTICS | BUGS | SEE ALSO

NAME

ifconfig- configure network interface parameters

SYNOPSIS

ifconfig interface address_family [address] [dest_address]
ifconfig -a [-d] [-u] [address_family]
ifconfig -l [-d] [-u] [address_family]

DESCRIPTION

The ifconfig command is available in two forms:

• as a C_INIT(1M) built-in command.

• as a standalone command.

The ifconfig command is used to assign an address to a network interface and/or configure network interface parameters. It must be used at boot time to define the network address of each interface present on a machine; it may also be used later to redefine an interface's address or other operating parameters.

The following options are available:

address

For the DARPA-Internet family, the address is either a host name present in the host name database hosts(4CC), or a DARPA Internet address expressed in the Internet standard "dot notation".

address_family

Specifies the address family which affects interpretation of the remaining parameters. As an interface can receive transmissions in differing protocols with different naming schemes, specifying the address family is recommended. The address or protocol family currently supported is inet.

dest_address

Specifies the address of the correspondent on the other end of a point-to-point link.

interface

This parameter is a string of the form name unit, for example, en0.

The following parameters may be set with ifconfig:

add

Another name for the alias parameter. Introduced for compatibility with BSD/OS.

alias

Establish an additional network address for this interface. This is sometimes useful when changing network numbers, while still wanting to accept packets addressed to the old interface. If the address is on the same subnet as the first network address for this interface, a netmask of 0xffffffff must be specified.

--alias

Remove the network address specified. This would be used if you incorrectly specified an alias, or it was no longer needed. If you have incorrectly set an NS address having the side effect of specifying the host portion, removing all NS addresses will allow you to respecify the host portion.

anycast

(Inet6 only) Specify that the address configured is an anycast address. Based on the current specification, only routers may configure anycast addresses. Anycast address will not be used as source address of any of outgoing IPv6 packets.

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.

broadcast

(Inet only) Specify the address to use to represent broadcasts to the network. The default broadcast address is the address with a host containing all 1's.

debug

Enable driver-dependent debugging code; usually, this turns on extra console error logging.

-debug

Disable driver dependent debugging code.

delete

Another name for the -alias parameter.

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.

metric n

Set the routing metric of the interface to n, the default is 0. Higher metrics have the effect of making a route less favorable; metrics are counted as addition hops to the destination network or host.

mtu n

Set the maximum transmission unit of the interface to n, default is interface specific. The mtu is used to limit the size of packets that are transmitted on an interface. Not all interfaces support setting the mtu, and some interfaces have range restrictions.

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 networks(4CC). 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 standard network portion, and the subnet field should be contiguous with the network portion.

prefixlen len

(Inet6 only) Specify that len bits are reserved for subdividing networks into sub-networks. The len must be integer, and for syntactical reason it must be between 0 to 128. It is almost always 64 under the current IPv6 assignment rule. If the parameter is ommitted, 64 is used.

remove

Another name for the -alias parameter.

link[0-2]

Enable special processing of the link level of the interface. These three options are interface specific in actual effect, however, they are in general used to select special modes of operation. An example of this is to enable SLIP compression, or to select the connector type for some Ethernet cards. Refer to the man page for the specific driver for more information.

-link[0-2]

Disable special processing at the link level with the specified interface.

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 previously marked down, the hardware will be re-initialized.

The ifconfig command 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.

If the driver does supports the media selection system, the supported media list will be included in the output.

If -L flag is supplied, address lifetime is displayed for IPv6 addresses, as time offset string.

Optionally, the -a flag may be used instead of an interface name. This flag instructs ifconfig to display information about all interfaces in the system. The -d flag limits this to interfaces that are down, and -u limits this to interfaces that are up.

The -l flag may be used to list all available interfaces on the system, with no other additional information. Use of this flag is mutually exclusive with all other flags and commands, except for -d (only list interfaces that are down) and -u (only list interfaces that are up).

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

ATTRIBUTES

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE	ATTRIBUTE VALUE
Interface Stability	Evolving

NOTES

The media selection system is relatively new and only some drivers support it (or have need for it).

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.

BUGS

IPv6 link-local addresses are required for several basic communication between IPv6 node. If they are deleted by ifconfig manually, the microkernel might show very strange behavior. So, such manual deletions are strongly discouraged.

SEE ALSO

netstat(1CC), route(1M), sysadm.ini(4CC)

NAME | SYNOPSIS | DESCRIPTION | ATTRIBUTES | NOTES | DIAGNOSTICS | BUGS | SEE ALSO