epair(4) A pair of virtual back-to-back connected Ethernet interfaces


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.conf5:



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

Each 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.conf5. While for cloning you only give either epair or epair<n> the pair will be named like epair<n>[ab] This means the names of the first interfaces will be epair0a and epair0b

Like any other Ethernet interface, an needs to have a network address. Each 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_bridge4 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.


The interface first appeared in Fx 8.0 .


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