man/man4/veth.4

.\" Copyright (c) 2012 Tomáš Pospíšek (tpo_deb@sourcepole.ch),
.\"     Fri, 03 Nov 2012 22:35:33 +0100
.\" and Copyright (c) 2012 Eric W. Biederman <ebiederm@xmission.com>
.\"
.\" SPDX-License-Identifier: GPL-2.0-or-later
.\"
.\"
.TH veth 4 (date) "Linux man-pages (unreleased)"
.SH NAME
veth \- Virtual Ethernet Device
.SH DESCRIPTION
The
.B veth
devices are virtual Ethernet devices.
They can act as tunnels between network namespaces to create
a bridge to a physical network device in another namespace,
but can also be used as standalone network devices.
.P
.B veth
devices are always created in interconnected pairs.
A pair can be created using the command:
.P
.in +4n
.EX
# ip link add <p1-name> type veth peer name <p2-name>
.EE
.in
.P
In the above,
.I p1-name
and
.I p2-name
are the names assigned to the two connected end points.
.P
Packets transmitted on one device in the pair are immediately received on
the other device.
When either device is down, the link state of the pair is down.
.P
.B veth
device pairs are useful for combining the network
facilities of the kernel together in interesting ways.
A particularly interesting use case is to place one end of a
.B veth
pair in one network namespace and the other end in another network namespace,
thus allowing communication between network namespaces.
To do this, one can provide the
.B netns
parameter when creating the interfaces:
.P
.in +4n
.EX
# ip link add <p1\-name> netns <p1\-ns> type veth peer <p2\-name> netns <p2\-ns>
.EE
.in
.P
or, for an existing
.B veth
pair, move one side to the other namespace:
.P
.in +4n
.EX
# ip link set <p2\-name> netns <p2\-ns>
.EE
.in
.P
.BR ethtool (8)
can be used to find the peer of a
.B veth
network interface, using commands something like:
.P
.in +4n
.EX
# \fBip link add ve_A type veth peer name ve_B\fP   # Create veth pair
# \fBethtool \-S ve_A\fP         # Discover interface index of peer
NIC statistics:
     peer_ifindex: 16
# \fBip link | grep \[aq]\[ha]16:\[aq]\fP   # Look up interface
16: ve_B@ve_A: <BROADCAST,MULTICAST,M\-DOWN> mtu 1500 qdisc ...
.EE
.in
.SH "SEE ALSO"
.BR clone (2),
.BR network_namespaces (7),
.BR ip (8),
.BR ip\-link (8),
.BR ip\-netns (8)