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LO(4) OpenBSD Programmer's Manual LO(4) NAME lo - software loopback network interface SYNOPSIS pseudo-device loop _number_ DESCRIPTION The loop interface is a software loopback mechanism which may be used for performance analysis, software testing, and/or local communication. As with other network interfaces, the loopback interface must have network addresses assigned for each address family with which it is to be used. These addresses may be set or changed with the SIOCSIFADDR ioctl(2). The loopback interface should be the last interface configured, as protocols may use the order of configuration as an indication of priority. The loopback should never be configured first unless no hardware interfaces exist. Configuring a loopback interface for inet(4) with the link1 flag set will make the interface answer to the whole set of addresses identified as be- ing in super-net which is specified by the address and netmask. Obvious- ly you should not set the link1 flag on interface lo0, but instead use another interface like lo1. EXAMPLES ifconfig lo1 inet 192.168.1.1 netmask 255.255.255.0 link1 is equivalent to: awk 'BEGIN {for(i=1;i<255;i++) print "ifconfig lo1 inet 192.168.1."i" netmask 255.255.255.255 alias"}'|sh DIAGNOSTICS lo%d: can't handle af%d. The interface was handed a message with ad- dresses formatted in an unsuitable address family; the packet was dropped. SEE ALSO inet(4), inet6(4), netintro(4), ns(4), ifconfig(8) HISTORY The lo device appeared in 4.2BSD. The wildcard functionality first appeared in OpenBSD 2.3. BUGS Previous versions of the system enabled the loopback interface automati- cally, using a non-standard Internet address (127.1). Use of that ad- dress is now discouraged; a reserved host address for the local network should be used instead. Care should be taken when using NAT with interfaces that have the link1 flag set, because it may believe the packets are coming from a loopback address. OpenBSD 3.4 June 5, 1993 1
NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | DIAGNOSTICS | SEE ALSO | HISTORY | BUGS
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