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ifconfig - configure network interface parameters
ifconfig interface [ [ alias | -alias ] address ]
[ netmask mask ] [ broadcast address ]
[ mediatype type ] [ mtusize size ] [ up | down ]
[ trusted | untrusted ]
ifconfig -a
ifconfig is used to assign an address to a network interface
and configure network interface parameters. ifconfig must
be used at boot time to define the network address of each
interface present on a machine; it may also be used at a
later time to redefine an interface's address or other
operating parameters. When used without optional parameters,
ifconfig displays the current configuration for a network
interface.
The interface parameter is the name of the network interface.
On EISA-based machines, that name is of the form nsn
for Ethernet interfaces and fin for FDDI interfaces, where n
is that interface's ordinal number (e.g., the first Ethernet
interface is ns0, the second is ns1, etc.). On PCI-based
machines, that name is of the form en for Ethernet interfaces,
fn for FDDI interfaces, and an for ATM interfaces,
possibly followed by a letter, where n is 0 for on-board
interfaces and the expansion slot number for interfaces
plugged into expansion slots. If a card in an expansion
slot has more than one interface, the interface name will be
followed by a letter between a and z indicating which of the
interfaces on that card it is. The interface name vh is
used to specify IP virtual host addresses associated with
the filer. Only alias addresses (using the alias option)
may be assigned to the vh interface. The interface name -a
is special and it does not take any optional parameters. It
displays the current configuration for all the network
interfaces present.
The address is either a host name present in the host name
data base /etc/hosts or an Internet address expressed in the
Internet standard dot notation.
broadcast address
Specifies the address to use to represent
broadcasts to the network. The default
broadcast address is the address with a host
part of all 1's.
- down
- Marks 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.
mediatype type Specifies the Ethernet media type used.
Depending on the physical specifications of
the Ethernet card the acceptable types are
"thick" (10Base5 AUI), "thin" (10Base2 BNC),
"tp" (10Base-T RJ-45 twisted-pair), or "tpfd"
(Full duplex 10Base-T RJ-45 twistedpair),
or "100tx" (100Base-T RJ-45 twistedpair),
or "100tx-fd" (Full duplex 100Base-T
RJ-45 twisted-pair), or "auto" (Auto RJ-45
twisted-pair). The default media type is
set to "tp" or to "auto" where applicable.
On a 10/100 Mbps auto-negotiable interface,
the system will auto-negotiate a 10 Mbps
half or full duplex or 100 Mbps half or full
duplex link and set the interface accordingly
when it is configured up. If the other
end does not support auto-negotiation and
full duplex operation is desired, it must be
explicitly set using the mediatype command.
On a 10/100 Mbps interface, the system will
auto-detect a 10 Mbps or 100 Mbps link and
set the link speed accordingly when the
interface is configured up. The hardware is
not currently capable of auto-detecting full
duplex interfaces, so if full duplex operation
is desired, it must be explicitly set
using the mediatype command. Only the
10/100 Mbps interfaces are capable of full
duplex operation.
- mtusize size
- Specifies the MTU (maximum transmission
unit) to use for the interface. This is
normally necessary only for non-compliant
FDDI or ATM bridges, routers or switches
that don't know how to fragment FDDI or ATM
size packets.
- netmask mask
- 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 /etc/networks. 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. A
default netmask is chosen according to the
class of the IP address.
- up
- Marks 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.
- alias
- Establishes an additional network address
for this interface. This is sometimes useful
when changing network numbers and one
wishes to accept packets addressed to the
old interface. It is required when creating
IP virtual host addresses.
- -alias
- Remove a network address for this interface.
- trusted
- Specifies that the network to which the
interface is attached is trusted relative to
firewall-style security (default).
- untrusted
- Specifies that the network to which the
interface is attached is not trusted relative
to firewall-style security.
- /etc/hosts
- host name data base
- /etc/networks
- network name data base
na_hosts(5), na_networks(5)
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