ifconfig(ADMN) 19 June 1992 ifconfig(ADMN) Name ifconfig - configure network interface parameters Syntax /etc/ifconfig interface addressfamily [ address [ destaddress ] ] [ parameters ] /etc/ifconfig interface [ protocolfamily ] Description ifconfig assigns an address to a network interface and/or configure net- work 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 oper- ating parameters. The interface parameter is a string of the form name unit, for example, ``en0''. Since an interface may receive transmissions in differing protocols, each of which may require separate naming schemes, it is necessary to specify the addressfamily, which may change the interpretation of the remaining parameters. Currently only the Internet address family is supported: thus, the only valid value for addressfamily is inet. For the DARPA-Internet family, the address is either a host name present in the host name data base, hosts(SFF), or a DARPA Internet address expressed in the Internet standard ``dot notation''. The following parameters may be set with ifconfig: up Mark an interface ``up''. This may be used to enable an interface after an ``ifconfig down.'' It happens automat- ically when setting the first address on an interface. If the interface was reset when previously marked down, the hardware will be re-initialized. down Mark 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. trailers Request the use of a ``trailer'' link level encapsulation when sending (default). If a network interface supports trailers, the system will, when possible, encapsulate out- going messages in a manner which minimizes the number of memory to memory copy operations performed by the receiver. On networks that support the Address Resolution Protocol (see arp(ADMP); currently, only 10 Mb/s Ether- net), this flag indicates that the system should request that other systems use trailers when sending to this host. Similarly, trailer encapsulations will be sent to other hosts that have made such requests. Currently used by Internet protocols only. -trailers Disable the use of a ``trailer'' link level encapsulation. arp Enable the use of the Address Resolution Protocol in map- ping between network level addresses and link level addresses (default). This is currently implemented for mapping between DARPA Internet addresses and 10Mb/s Ether- net addresses. This option is not applicable in the STREAMS environment. Use of arp for an interface is specified in /etc/strcf. The arp driver will be opened when the STREAMS stack is built. -arp Disable the use of the Address Resolution Protocol. metric n Set the routing metric of the interface to n, default 0. The routing metric is used by the routing protocol routed(ADMN)). Higher metrics have the effect of making a route less favorable; metrics are counted as addition hops to the destination network or host. debug Enable driver dependent debugging code; usually, this turns on extra console error logging. -debug Disable driver dependent debugging code. netmask mask (inet only) Specify how much of the address to reserve for subdividing networks into sub-networks. 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(SFF). The mask contains 1's for the bit posi- tions in the 32-bit address which 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. destaddress Specify the address of the correspondent on the other end of a point to point link. broadcast (inet only) Specify the address to use to represent broad- casts to the network. The default broadcast address is the address with a host part of all 1's. onepacket Enable the one-packet mode of operation (used for inter- faces that can't handle back-to-back packets). The key- word onepacket must be followed by two numeric parameters, giving the small packet size and threshold, respectively. If small packet detection is not desired, these values should be zero. See tcp(ADMP) for an explanation of one- packet mode. -onepacket Disable one-packet mode. ifconfig displays the current configuration for a network interface when no optional parameters are supplied. If a protocol family is specified, ifconfig will report only the details specific to that protocol family. Only the super-user may modify the configuration of a network interface. Diagnostics ifconfig has no error messages indicating the specified interface does not exist, or the requested address is unknown, or the user is not privileged and tried to alter an interface's configuration. See also arp(ADMN), tcp(ADMN), netstat(TC), hosts(SFF), networks(SFF), strcf(SFF), arp(ADMP), Intro(ADMP), tcp(ADMP)