NAME


ifconfig - configure a network interface

SYNOPSIS


ifconfig [interface] ifconfig interface [aftype] options | address ...

DESCRIPTION


Ifconfig is used to configure the kernel-resident network interfaces. It is used at boot time to set up interfaces as necessary. After that, it is usually only needed when debugging or when system tuning is needed.

WARNING: Ifconfig is obsolete on system with Linux kernel newer than 2.0. On this system you should use ip. See the ip manual page for details

If no arguments are given, ifconfig displays the status of the currently active interfaces. If a single interface argument is given, it displays the status of the given interface only; if a single -a argument is given, it displays the status of all interfaces, even those that are down. Otherwise, it configures an interface.

Address Families


If the first argument after the interface name is recognized as the name of a supported address family, that address family is used for decoding and displaying all protocol addresses. Currently supported address families include inet (TCP/IP, default), inet6 (IPv6), ax25 (AMPR Packet Radio), ddp (Appletalk Phase 2), ipx (Novell IPX) and netrom (AMPR Packet radio).

OPTIONS


interface
 The name of the interface. This is usually a driver name followed by a unit number, for example eth0 for the first Ethernet interface.
up This flag causes the interface to be activated. It is implicitly specified if an address is assigned to the interface.
down This flag causes the driver for this interface to be shut down.
[-]arp Enable or disable the use of the ARP protocol on this interface.
[-]promisc
 Enable or disable the promiscuous mode of the interface. If selected, all packets on the network will be received by the interface.
[-]allmulti
 Enable or disable all-multicast mode. If selected, all multicast packets on the network will be received by the interface.
metric N
 This parameter sets the interface metric.
mtu N This parameter sets the Maximum Transfer Unit (MTU) of an interface.
dstaddr addr
 Set the remote IP address for a point-to-point link (such as PPP). This keyword is now obsolete; use the pointopoint keyword instead.
netmask addr
 Set the IP network mask for this interface. This value defaults to the usual class A, B or C network mask (as derived from the interface IP address), but it can be set to any value.
add addr/prefixlen
 Add an IPv6 address to an interface.
del addr/prefixlen
 Remove an IPv6 address from an interface.
tunnel aa.bb.cc.dd
 Create a new SIT (IPv6-in-IPv4) device, tunnelling to the given destination.
irq addr
 Set the interrupt line used by this device. Not all devices can dynamically change their IRQ setting.
io_addr addr
 Set the start address in I/O space for this device.
mem_start addr
 Set the start address for shared memory used by this device. Only a few devices need this.
media type
 Set the physical port or medium type to be used by the device. Not all devices can change this setting, and those that can vary in what values they support. Typical values for type are 10base2 (thin Ethernet), 10baseT (twisted-pair 10Mbps Ethernet), AUI (external transceiver) and so on. The special medium type of auto can be used to tell the driver to auto-sense the media. Again, not all drivers can do this.
[-]broadcast [addr]
 If the address argument is given, set the protocol broadcast address for this interface. Otherwise, set (or clear) the IFF_BROADCAST flag for the interface.
[-]pointopoint [addr]
 This keyword enables the point-to-point mode of an interface, meaning that it is a direct link between two machines with nobody else listening on it. If the address argument is also given, set the protocol address of the other side of the link, just like the obsolete dstaddr keyword does. Otherwise, set or clear the IFF_POINTOPOINT flag for the interface.
hw class address
 Set the hardware address of this interface, if the device driver supports this operation. The keyword must be followed by the name of the hardware class and the printable ASCII equivalent of the hardware address. Hardware classes currently supported include ether (Ethernet), ax25 (AMPR AX.25), ARCnet and netrom (AMPR NET/ROM).
multicast
 Set the multicast flag on the interface. This should not normally be needed as the drivers set the flag correctly themselves.
address
 The IP address to be assigned to this interface.
txqueuelen length
 Set the length of the transmit queue of the device. It is useful to set this to small values for slower devices with a high latency (modem links, ISDN) to prevent fast bulk transfers from disturbing interactive traffic like telnet too much.

NOTES


Since kernel release 2.2 there are no explicit interface statistics for alias interfaces anymore. The statistics printed for the original address are shared with all alias addresses on the same device. If you want per-address statistics you should add explicit accounting rules for the address using the ipchains(8) command.

Interrupt problems with Ethernet device drivers fail with EAGAIN. See http://cesdis.gsfc.nasa.gov/linux/misc/irq-conflict.html for more information.

FILES


/proc/net/socket
/proc/net/dev
/proc/net/if_inet6

BUGS


While appletalk DDP and IPX addresses will be displayed they cannot be altered by this command.

SEE ALSO


route(8), netstat(8), arp(8), rarp(8), ipchains(8)

AUTHORS


Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org> Alan Cox, <Alan.Cox@linux.org> Phil Blundell, <Philip.Blundell@pobox.com> Andi Kleen

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