NAME

ifconfig − configure network interface parameters

SYNOPSIS

/etc/ifconfig interface [Ethernet_address] [hostname] [parameters]

DESCRIPTION

ifconfig is used to assign an address to a network interface and/or to configure network interface parameters.  ifconfig is used at boot time to define the network address of each interface present on a machine.  You can use ifconfig 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.  Only the super-user may modify the configuration of a network interface. 

The interface parameter is a string of the form name_unit , for example, ie0. 

OPTIONS

Ethernet_addressThe hardware Ethernet address of a given machine.  The address is a six-byte hexadecimal value; each byte of the address is separated by a colon.  A typical Ethernet adddress is 8:0:20:1:1:A3.  This address is contained in the ID PROM on the Sun CPU Board, and is reported at boot time as one of the PROM monitor’s sign-on messages.  The Ethernet_address option is normally not used—the hardware supplies the default.  Use the option only when trying to talk to a device that does not support ARP. 

hostnameMay be either the hostname of a given machine (present in the hostname database, hosts(5)), or the complete Internet address consisting of your system’s network number and the machine’s unique host number. A typical Internet address might be 192.9.200.44, where 192.9.200 is the network number, and 44 is the machine’s hostnumber.  To find a machine’s Internet address, consult the local /etc/hosts file. 

PARAMETERS

The following parameters may be set with ifconfig :

upMarks an interface “up.” You can use it to enable an interface after an “ifconfig down.” It happens automatically when you set the first address on an interface.  If the interface was reset when previously marked down, the hardware will be re-initialized. 

downMarks an interface “down.” When an interface is marked down, the system does not attempt to transmit messages through that interface.  If possible, the interface is reset to disable reception, as well.  This action does not automatically disable routes using the interface. 

trailersEnables the use of a “trailer” link level encapsulation when sending messages (the default).  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. This feature is machine-dependent, and therefore not recommended.

-trailersDisables the use of a “trailer” link level encapsulation. 

arpEnables 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. 

-arpDisables the use of the Address Resolution Protocol. 

netmask maskSpecifies 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.  You can specify the mask 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(5). The mask contains 1’s for the bit positions in the 32-bit address that 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.

broadcast addressSpecifies 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. 

EXAMPLE

If your workstation is not attached to an Ethernet, you should mark down the ie0 interface as follows:

ifconfig ie0 down

DIAGNOSTICS

Messages indicating that the specified interface does not exist, that the requested address is unknown, or that a user without proper privileges tried to alter an interface’s configuration. 

SEE ALSO

rc(8), intro(3N), netstat(8C)

Sun Release 3.4  —  Last change: 3 October 1986