PAIR(4) FreeBSD Kernel Interfaces Manual PAIR(4)
NAME
pair - virtual Ethernet interface pair
SYNOPSIS
pseudo-device pair
DESCRIPTION
The pair interface simulates a normal Ethernet interface by encapsulating
standard network frames with an Ethernet header, specifically for use in
a pair of interfaces that are interconnected with each other.
To use it, the administrator needs to create two pair interfaces and
connect them; the interfaces are `patched', as would be done with
physical network ports. All packets that are sent on the first interface
are received on the second interface.
EXAMPLES
Set up a pair of interfaces where each of them is a member of a different
rdomain(4):
# ifconfig pair1 rdomain 1 10.1.1.1/24 up
# ifconfig pair2 rdomain 2 10.1.1.2/24 up
# ifconfig pair1 patch pair2
# route -T 1 exec ping 10.1.1.2
When adding multiple pair to multiple bridge(4) interfaces, it is
possible to create a loop; the system load will go up while it is busy
sending packets from one bridge to another and back. By design, the
driver does not prevent such loops by itself, but it is possible to use
the Spanning Tree Protocol (STP) to detect and remove loops in the
virtual network topology:
# ifconfig pair0 up
# ifconfig pair1 rdomain 1 patch pair0 up
# ifconfig pair2 up
# ifconfig pair3 rdomain 1 patch pair2 up
# ifconfig bridge0 add pair0 add pair2 stp pair0 stp pair2 up
# ifconfig bridge1 add pair1 add pair3 stp pair1 stp pair3 up
SEE ALSO
bridge(4), inet(4), inet6(4), rdomain(4), vether(4), hostname.if(5),
ifconfig(8), netstart(8)
HISTORY
The pair interface first appeared in OpenBSD 5.9.
AUTHORS
The pair driver is based on vether(4) by Theo de Raadt
<
[email protected]>. It has been extended and turned into pair by
Reyk Floeter <
[email protected]>.
CAVEATS
Unlike vether(4), the pair interface cannot be used as a stand-alone
member in a bridge(4): the link state remains down until it is connected
to the second interface. Any associated routes will be marked down until
it is patched. Use vether(4) as a bridge endpoint for routing purposes
instead.
BUGS
Like tun(4), the Ethernet address chosen will be partially random, and
may occasionally collide with another address.
FreeBSD 14.1-RELEASE-p8 October 30, 2015 FreeBSD 14.1-RELEASE-p8