ifconfig(8)

NAME
ifconfig - network interface configuration

SYNOPSIS
ifconfig [-a|-v] [interface options]

DESCRIPTION
Ifconfig is used to set and show the addresses, flags and options of network interfaces.

When ifconfig is invoked without arguments, it shows a table of all running network interfaces, their addresses and flags in a human readable form. The option -a forces ifconfig to display all interfaces in the system, no matter if they are running or not.

When a single argument (the name of a network interface) is given, ifconfig just shows the status of this interface.

ifconfig sets flags and addresses of the interface named as the first argument when additional options are given.

OPTIONS

interface
    The name of the interface to deal with. lo0, and sl0 are valid names for the loopback interface and the SLIP interface (channel 0) respectively.

addr inetaddr
    This option causes ifconfig to set the local IP address of the interface to inetaddr. This is the address your machine can be reached at over this interface. inetaddr can be in standard IP address dot notation or can be a symbolic name which is resolved into an IP address. NOTE that you must not use a symbolic name when setting up the loopback interface, because symbolic names cannot be resolved before the loopback interface is set up.

dstaddr inetaddr
    Set the point to point destination address of the interface to inetaddr, which can be an IP address or a symbolic name. This option will only work on point to point interfaces, like the sl? ones.

broadaddr aa.bb.cc.dd
    Set the broadcast address of the interface to aa.bb.cc.dd. This defaults to the net broadcast address of the attached network, but can be set to any valid IP address. This option will only work on interfaces that support broadcasting, like the lo0 interface.

netmask aa.bb.cc.dd
    Set the subnet mask of the interface to aa.bb.cc.dd. This is by default the class A, B or C netmask of the local address of the interface set with the addr option. It can be used to split a large network into many small subnetworks.

up  This sets the UP flag on the interface. This is used to activate the interface.

down
    This clears the UP flags on the interface. This is used to shut down the interface.

[-]arp
    (De)activate usage of the ARP (address resolution protocol) protocol for resolving IP addresses into hardware addresses.

[-]trailers
    (De)activate usage of trailer encapsulation for this interface.

[-]debug
    (De)activate debugging for this interface. Debugging is currently a no-op.

mtu NN
    Set the mtu (maximum transmission unit) of the interface to NN bytes. Better make it large enough as long as fragmentation is not implemented.

metric NN
    Set the metric of the interface to NN. This value is currently not used.

[-]linkNN
    This option sets (clears) the bit with number NN in the link level flag word of the interface. The flag word is 16 bits wide, so [-]link0 through [-]link15 are valid. Bit 0 is the least significant, bit 15 the most significant bit.
    Link level flags are interface type specific. Thats why ifconfig only uses bit numbers instead of meaningful names for them. Currently only SLIP interfaces support link level flags. Bit 3 turns auto compression on: if set and a VJ compressed SLIP frame is received the interface enables compression for outgoing frames. Bit 4 is the compression bit: if set VJ header compression is enabled.

AUTHOR
Kay Roemer <roemer@rbi.informatik.uni-frankfurt.de>

SEE ALSO
route(8).