ifconfig(8c)ifconfig(8c)Nameifconfig - configure network interface parameters
/etc/ifconfig interface [ address [ dest_address ] ] [ parameters ]
The command assigns an address to a network interface and/or configures
network interface parameters. You must use 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 inter‐
face 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,
or a DARPA Internet address expressed in the Internet standard dot
You can set the following parameters with
up Marks an interface up.
down Marks an interface down. When an interface is marked down,
the system does not attempt to transmit messages through that
trailers Enables the use of a trailer link level encapsulation when
sending. If a network interface supports trailers, the sys‐
tem, when possible, encapsulates outgoing messages in a man‐
ner that minimizes the number of memory-to-memory copy opera‐
tions 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 -trail‐
-trailers Disables the use of a trailer link level encapsulation. This
is the recommended setting.
promisc Enables the use of the in the promiscuous mode. The promiscu‐
ous mode allows the network interface to receive all the
packets off the wire and pass it onto to the packet filter.
-promisc Disables the promiscuous mode of the packet filter. This is
+copyall Sets 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).
-copyall Disables copy-all mode. (See for more information aboutut the
arp Enables 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 map‐
ping between DARPA Internet addresses and 10Mb/s Ethernet
-arp Disables the use of the Address Resolution Protocol.
debug Enables driver-dependent debugging code. Usually, this turns
on extra console error logging.
-debug Disables driver dependent debugging code.
netmask Specifies how many bits of the address you wish to reserve
for subdividing Class A and B networks into sub-networks.
dstaddr Specifies the correspondent on the other end of a point to
broadcast Specifies the address you wish to use to represent broadcasts
to the network.
The 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.
The 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.
See Alsonetstat(1), intro(4n), packetfilter(4), MAKEDEV(8), pfconfig(8c), pfs‐