xref: /linux/Documentation/networking/vxlan.rst (revision 33a1aaf8) 
1.. SPDX-License-Identifier: GPL-2.0
2
3======================================================
4Virtual eXtensible Local Area Networking documentation
5======================================================
6
7The VXLAN protocol is a tunnelling protocol designed to solve the
8problem of limited VLAN IDs (4096) in IEEE 802.1q.  With VXLAN the
9size of the identifier is expanded to 24 bits (16777216).
10
11VXLAN is described by IETF RFC 7348, and has been implemented by a
12number of vendors.  The protocol runs over UDP using a single
13destination port.  This document describes the Linux kernel tunnel
14device, there is also a separate implementation of VXLAN for
15Openvswitch.
16
17Unlike most tunnels, a VXLAN is a 1 to N network, not just point to
18point. A VXLAN device can learn the IP address of the other endpoint
19either dynamically in a manner similar to a learning bridge, or make
20use of statically-configured forwarding entries.
21
22The management of vxlan is done in a manner similar to its two closest
23neighbors GRE and VLAN. Configuring VXLAN requires the version of
24iproute2 that matches the kernel release where VXLAN was first merged
25upstream.
26
271. Create vxlan device::
28
29    # ip link add vxlan0 type vxlan id 42 group 239.1.1.1 dev eth1 dstport 4789
30
31This creates a new device named vxlan0.  The device uses the multicast
32group 239.1.1.1 over eth1 to handle traffic for which there is no
33entry in the forwarding table.  The destination port number is set to
34the IANA-assigned value of 4789.  The Linux implementation of VXLAN
35pre-dates the IANA's selection of a standard destination port number
36and uses the Linux-selected value by default to maintain backwards
37compatibility.
38
392. Delete vxlan device::
40
41    # ip link delete vxlan0
42
433. Show vxlan info::
44
45    # ip -d link show vxlan0
46
47It is possible to create, destroy and display the vxlan
48forwarding table using the new bridge command.
49
501. Create forwarding table entry::
51
52    # bridge fdb add to 00:17:42:8a:b4:05 dst 192.19.0.2 dev vxlan0
53
542. Delete forwarding table entry::
55
56    # bridge fdb delete 00:17:42:8a:b4:05 dev vxlan0
57
583. Show forwarding table::
59
60    # bridge fdb show dev vxlan0
61
62The following NIC features may indicate support for UDP tunnel-related
63offloads (most commonly VXLAN features, but support for a particular
64encapsulation protocol is NIC specific):
65
66 - `tx-udp_tnl-segmentation`
67 - `tx-udp_tnl-csum-segmentation`
68    ability to perform TCP segmentation offload of UDP encapsulated frames
69
70 - `rx-udp_tunnel-port-offload`
71    receive side parsing of UDP encapsulated frames which allows NICs to
72    perform protocol-aware offloads, like checksum validation offload of
73    inner frames (only needed by NICs without protocol-agnostic offloads)
74
75For devices supporting `rx-udp_tunnel-port-offload` the list of currently
76offloaded ports can be interrogated with `ethtool`::
77
78  $ ethtool --show-tunnels eth0
79  Tunnel information for eth0:
80    UDP port table 0:
81      Size: 4
82      Types: vxlan
83      No entries
84    UDP port table 1:
85      Size: 4
86      Types: geneve, vxlan-gpe
87      Entries (1):
88          port 1230, vxlan-gpe
89