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NAME

     epair — A pair of virtual back-to-back connected Ethernet interfaces.

SYNOPSIS

     To compile this driver into the kernel, place the following line in your kernel
     configuration file:

           device epair

     Alternatively, to load the driver as a module at boot time, place the following line in
     loader.conf(5):

           if_epair_load="YES"

DESCRIPTION

     The epair is a pair of Ethernet-like software interfaces, which are connected back-to-back
     with a virtual cross-over cable.

     Each epair interface pair is created at runtime using interface cloning.  This is most
     easily done with the ifconfig(8) create command or using the cloned_interfaces variable in
     rc.conf(5).  While for cloning you only give either epair or epair<n> the epair pair will be
     named like epair<n>[ab].  This means the names of the first epair interfaces will be epair0a
     and epair0b.

     Like any other Ethernet interface, an epair needs to have a network address.  Each epair
     will be assigned a locally administered address by default, that is only guaranteed to be
     unique within one network stack.  To change the default addresses one may use the
     SIOCSIFADDR ioctl(2) or ifconfig(8) utility.

     The basic intend is to provide connectivity between two virtual network stack instances.
     When connected to a if_bridge(4) one end of the interface pair can also be part of another
     (virtual) LAN.  As with any other Ethernet interface one can configure vlan(4) support on
     top of it.

SEE ALSO

     ioctl(2), altq(4), bpf(4), if_bridge(4), vlan(4), loader.conf(5,) rc.conf(5), ifconfig(8)

HISTORY

     The epair interface first appeared in FreeBSD 8.0.

AUTHORS

     The epair interface was written by Bjoern A. Zeeb, CK Software GmbH, under sponsorship from
     the FreeBSD Foundation.