man4/veth.4

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  28 .TH VETH 4 2018-02-02 "Linux" "Linux Programmer's Manual"
  29 .SH NAME
  30 veth \- Virtual Ethernet Device
  31 .SH DESCRIPTION
  32 The
  33 .B veth
  34 devices are virtual Ethernet devices.
  35 They can act as tunnels between network namespaces to create
  36 a bridge to a physical network device in another namespace,
  37 but can also be used as standalone network devices.
  38 .PP
  39 .B veth
  40 devices are always created in interconnected pairs.
  41 A pair can be created using the command:
  42 .PP
  43 .in +4n
  44 .EX
  45 # ip link add <p1-name> type veth peer name <p2-name>
  46 .EE
  47 .in
  48 .PP
  49 In the above,
  50 .I p1-name
  51 and
  52 .I p2-name
  53 are the names assigned to the two connected end points.
  54 .PP
  55 Packets transmitted on one device in the pair are immediately received on
  56 the other device.
  57 When either devices is down the link state of the pair is down.
  58 .PP
  59 .B veth
  60 device pairs are useful for combining the network
  61 facilities of the kernel together in interesting ways.
  62 A particularly interesting use case is to place one end of a
  63 .B veth
  64 pair in one network namespace and the other end in another network namespace,
  65 thus allowing communication between network namespaces.
  66 To do this, one can provide the
  67 .B netns
  68 parameter when creating the interfaces:
  69 .PP
  70 .in +4n
  71 .EX
  72 # ip link add <p1-name> netns <p1-ns> type veth peer <p2-name> netns <p2-ns>
  73 .EE
  74 .in
  75 .PP
  76 or, for an existing
  77 .B veth
  78 pair, move one side to the other namespace:
  79 .PP
  80 .in +4n
  81 .EX
  82 # ip link set <p2-name> netns <p2-ns>
  83 .EE
  84 .in
  85 .PP
  86 .BR ethtool (8)
  87 can be used to find the peer of a
  88 .B veth
  89 network interface, using commands something like:
  90 .PP
  91 .in +4n
  92 .EX
  93 # \fBip link add ve_A type veth peer name ve_B\fP   # Create veth pair
  94 # \fBethtool -S ve_A\fP         # Discover interface index of peer
  95 NIC statistics:
  96      peer_ifindex: 16
  97 # \fBip link | grep '^16:'\fP   # Look up interface
  98 16: ve_B@ve_A: <BROADCAST,MULTICAST,M-DOWN> mtu 1500 qdisc ...
  99 .EE
 100 .in
 101 .PP
 102 .SH "SEE ALSO"
 103 .BR clone (2),
 104 .BR network_namespaces (7),
 105 .BR ip (8),
 106 .BR ip-link (8),
 107 .BR ip-netns (8)