man4/veth.4

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  26 .TH veth 4 2017-10-03 "Linux" "Linux Programmer's Manual"
  27 .SH NAME
  28 veth \- Virtual Ethernet Device
  29 .SH DESCRIPTION
  30 The
  31 .B veth
  32 devices are virtual Ethernet devices.
  33 They can act as tunnels between network namespaces to create
  34 a bridge to a physical network device in another namespace,
  35 but can also be used as standalone network devices.
  36 .PP
  37 .B veth
  38 devices are always created in interconnected pairs.
  39 A pair can be created using the command:
  40 .PP
  41 .in +4n
  42 .EX
  43 # ip link add <p1-name> type veth peer name <p2-name>
  44 .EE
  45 .in
  46 .PP
  47 In the above,
  48 .I p1-name
  49 and
  50 .I p2-name
  51 are the names assigned to the two connected end points.
  52 .PP
  53 Packets transmitted on one device in the pair are immediately received on
  54 the other device.
  55 When either devices is down the link state of the pair is down.
  56 .PP
  57 .B veth
  58 device pairs are useful for combining the network
  59 facilities of the kernel together in interesting ways.
  60 A particularly interesting use case is to place one end of a
  61 .B veth
  62 pair in one network namespace and the other end in another network namespace,
  63 thus allowing communication between network namespaces.
  64 To do this, one first creates the
  65 .B veth
  66 device as above and then moves one side of the pair to the other namespace:
  67 .PP
  68 .in +4n
  69 .EX
  70 # ip link set <p2-name> netns <p2-namespace>
  71 .EE
  72 .in
  73 .PP
  74 .BR ethtool (8)
  75 can be used to find the peer of a
  76 .B veth
  77 network interface, using commands something like:
  78 .PP
  79 .in +4n
  80 .EX
  81 # \fBip link add ve_A type veth peer name ve_B\fP   # Create veth pair
  82 # \fBethtool -S ve_A\fP         # Discover interface index of peer
  83 NIC statistics:
  84      peer_ifindex: 16
  85 # \fBip link | grep '^16:'\fP   # Look up interface
  86 16: ve_B@ve_A: <BROADCAST,MULTICAST,M-DOWN> mtu 1500 qdisc ...
  87 .EE
  88 .in
  89 .PP
  90 .SH "SEE ALSO"
  91 .BR clone (2),
  92 .BR ip (8),
  93 .BR ip-link (8),
  94 .BR ip-netns (8)