ifconfig(1M) ifconfig(1M) NAME ifconfig - configure network interface parameters SYNOPSIS /usr/etc/ifconfig [ -v ] interface address_family [ address [ dest_address ] ] [ parameters ] /usr/etc/ifconfig interface [ protocol_family ] /usr/etc/ifconfig [ -v ] -a DESCRIPTION ifconfig is used to assign an address to a network interface and/or configure network interface parameters. ifconfig is invoked at boot time from /etc/init.d/network to define the network address of each interface present on a machine; you can also use it once the system is up to redefine an interface's address or other operating parameters. The interface parameter is a string of the form ``name unit'', for example, enp0. Using the -a option shows status for all interfaces on the machine. If specified, the -v option causes additional information about specified interfaces to be displayed, including speed. Since an interface can receive transmissions in differing protocols, each of which may require separate naming schemes, it is necessary to specify the address_family, which can change the interpretation of the remaining parameters. Currently, the ``inet'' and ``inet6'' address families are supported. For the Internet Version 4 family, the address is either an Internet address expressed in the Internet standard ``dot notation'' (see inet(3N)), or a hostname present in the hosts(4) file, /etc/hosts. (Other hosts databases, such as named and NIS, are ignored.) For the Internet Version 6 family, the address is either expressed in the Internet standard ``colon notation'' (see inet6(3N)), or as a hostname. Only the superuser can modify the configuration of a network interface. The following parameters can be set with ifconfig: up Mark an interface up. This can 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 is reinitialized. down Mark an interface down. When an interface is marked down, the system does not attempt to transmit messages through that interface. If possible, the interface is reset to disable reception as well. This action does not automatically disable routes using the interface. Packets which have been queued for transmission may be dropped. arp Enable the use of the Address Resolution Protocol in mapping between network level addresses and link level addresses (default). It is used by a variety of data link network interfaces such as Ethernet. -arp Disable the use of the Address Resolution Protocol. alias addr Establish an additional network address for this interface. This can be useful in permitting a single physical interface to accept packets addressed to several different addresses such as when you are changing network numbers and you wish to accept packets addressed to the old interface. Another case is when you'd like to have multiple addresses assigned to a single network interface. The broadcast and netmask options can also be used in conjunction with the alias option. When using aliases you may have to change the configuration of routed, especially if aliases are on different networks than the primary address. Aliases are added as host entries in the routing tables for routed. See routed(1M) for more information on this. -alias|delete addr Deletes a previously added alias. metric n Set the routing metric of the interface to n, default 0. The routing metric is used by the routing protocol (routed). Higher metrics have the effect of making a route less favorable; metrics are counted as addition hops to the destination network or host. netmask mask Specify how much of the address to reserve for subdividing networks into subnetworks. 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 networks(4). 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. prefixlen len Specify the prefix length of the address. For use with inet6 addresses only. The prefix length is expressed as a non-negative integer, less than or equal to 128. It represents the number of bits in the address which are to be interpreted as a prefix. It is also possible to specify the prefix length using the slash notation, for example, 3ffe:100::a00:69ff:fe02:a2e7/64. mtu n Specify device maximum transmission unit value. This may not be supported on all devices and some devices may only offer limited support. Often, this is used to lower ethernet MTU's below 1500 bytes to interoperate with buggy adapters and network hardware. Also, on some gigabit interfaces it can be used to increase the MTU to 9000 to implement jumbo frames. broadcast addr Specify 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. dest_addr Specify the address of the correspondent on the other end of a point-to-point link. debug Enable driver-dependent debugging code; usually, this turns on extra console error logging. -debug Disable driver-dependent debugging code. highbw Flag an interface as being a high-bandwidth interface. This acts as a hint which allows upper layer protocols to adjust their behaviour to optimise performance (e.g. TCP will be less aggressive with ACKing). -highbw Remove the high-bandwidth flag from an interface. link{0,1,2} Enable driver-specific feature 0-2. -link{0,1,2} Disable driver-specific feature 0-2. primary This parameter makes the specified interface the primary interface for networking. In cases where no interface or interface address is specified by an application, the 'primary' interface will be preferred. rspace value Specifies the default receive space used by TCP when communicating over the interface. Use a value of 0 to clear this parameter and use the system-wide default. sspace value Specifies the default send space used by TCP when communicating over the interface. Use a value of 0 to clear this parameter and use the system-wide default. route Turn on the flag which indicates the system is routing on the specified interface. This is useful only for interfaces which have inet6 addresses and will cause neighbor advertisements from the interface to have the "IsRouter" flag set (if the system is configured as a router). (By default all interfaces will have this flag set at boot time if the system is configured as a router and all interfaces will have this flag cleared at boot time if configured as a host.) -route Turn off the flag which indicates the system is routing on the specified interface. This is useful only for interfaces which have inet6 addresses and will cause neighbor advertisements from the interface to have the "IsRouter" flag cleared. stripe laddr raddr Add a physical link to a stripe interface where laddr is the local link interface address and raddr is the remote link interface address. This command only applies to stripe interfaces. Refer to the NOTES section below for details. -stripe laddr Remove a physical link from a stripe interface where laddr matches the local link address of the link to be removed. This command only applies to stripe interfaces. stripelist List all of the addresses for the physical links configured on a stripe interface. The same link information is output when using verbose ( -v ) output. This command only applies to stripe interfaces. ifconfig displays the current configuration for a network interface when no optional parameters are supplied. If a protocol family is specified, ifconfig reports only the details specific to that protocol family. NOTES Network interfaces on Silicon Graphics systems can only receive and not send packets that use ``trailer'' link-level encapsulation. Therefore, ifconfig does not accept the trailers parameter. For 100baseTX interfaces, such as 'ef', LINK0 being set indicates that the device is operating at full-duplex. It is not currently possible to force full- or half-duplex by setting or clearing this flag. Currently options such as 'metric' are not handled for IP aliases; adjusting the metric will affect only the primary address. 'broadcast' and 'netmask' are the only options currently known to work properly with IP aliases. From 6.5.23, Irix supports Network Striping interfaces which allow multiple physical interfaces to be combined at the IP layer into a logical, routable interface called a stripe. For more details see the Irix 6.5.23 release of Irix Admin: Network and Mail. DIAGNOSTICS Messages indicating the specified interface does not exist, the requested address is unknown, or the user is not privileged and tried to alter an interface's configuration. FILES /etc/hosts host-address database /etc/config/ifconfig-?.options site-specific options (1 file per interface) /etc/config/ipaliases.options interface-specific ip alias addresses SEE ALSO netstat(1), network(1M). Page 5