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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.