NAME

ifconfig − configure network interface parameters

SYNOPSIS

ifconfig interface [ address | address netmask mask ] [ parameters ]

DESCRIPTION

Ifconfig is used to assign an address to a network interface and 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 can also be used at a later time to redefine an interface’s address. 

Interface is a string of the form “name unit,” such as, lan0, where “name” denotes the network interface and “unit” denotes the logical unit number. (See DEPENDENCIES to determine the logical unit number.) 

Address is either a host name present in the host name data base, hosts(4), or a DARPA Internet address expressed in the Internet standard dot notation. All numbers supplied as “parts” in dot notation can be decimal, octal, or hexadecimal as used in the C language (in other words, a leading 0x or 0X implies hexadecimal; a leading 0 implies octal; otherwise, the number is interpreted as decimal).

Netmask specifies how much of the address to reserve for subdividing the networks into subnetworks. In order to specify a netmask, a non-zero address followed by the keyword netmask followed by a mask value must be given. The mask includes the network part of the local address and the subnet part taken from the host field of the address. The mask can be specified as a single hexadecimal address with a leading 0x, with a dot notation internet address, or with a pseudo-network name listed in the network name data base, networks(4). The mask contains 1’s for the bit positions to be used as network and subnetwork parts and 0’s for the host part. For example, the mask, “0xfffff800” has 11 least-significant bits for the host part and 21 most-significant bits for the network/subnet part. The mask should contain at least the standard network part and the subnet field should be contiguous with the network portion.

The following parameters can 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. 

ieee Enables IEEE 802.3 protocol over the network interface. 

-ieee Disables IEEE 802.3 protocol over the network interface. 

ether Enables Ethernet protocol over the network interface. 

-ether Disables Ethernet protocol over the network interface. 

Ifconfig displays the current configuration for a network interface when no optional parameters are supplied. 

Only the super-user may modify the configuration of a network interface. 

Default flag settings: When you first configure a node on a network after installing the network software, the default ifconfig flag settings are: down, ieee and ether.  The up flag will be turned on after ifconfig is done with a non-zero Internet address. If you use ifconfig to reset an address (specifying a valid Internet address) without specifying any other parameters, the interface is set “up.” Prior values of other flags return to the default setting for the Series 800 and don’t change for the Series 300. 

DIAGNOSTICS

Messages indicate: 1) the specified interface does not exist, 2) the requested address is unknown, or 3) the user is not privileged and tried to alter an interface’s configuration. 

WARNINGS

Setting the up flag on an interface having a zero Internet address results in the interface being marked down.  You must execute the ifconfig command once for each configured network interface. 

DEPENDENCIES

The logical unit of the card is determined as follows:

Series 300 only: The LAN card with the lowest select code is given the logical unit number 0; the LAN card with the next higher select code is given the logical unit number 1; and so on. 

Series 800 only: HP recommends that the LAN card in the lowest slot in the backplane be assigned LAN0;  the card in the next highest slot be assigned LAN1;  and so on.  A maximum of three LAN cards are supported in the backplane. 

AUTHOR

UCB (University of California at Berkeley)

SEE ALSO

hosts(4), netstat(1), routing(7). 

Hewlett-Packard Company  —  May 11, 2021