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+.. _vxlan-interface:
+
+#####
+VXLAN
+#####
+
+:abbr:`VXLAN (Virtual Extensible LAN)` is a network virtualization technology
+that attempts to address the scalability problems associated with large cloud
+computing deployments. It uses a VLAN-like encapsulation technique to
+encapsulate OSI layer 2 Ethernet frames within layer 4 UDP datagrams, using
+4789 as the default IANA-assigned destination UDP port number. VXLAN
+endpoints, which terminate VXLAN tunnels and may be either virtual or physical
+switch ports, are known as :abbr:`VTEPs (VXLAN tunnel endpoints)`.
+
+VXLAN is an evolution of efforts to standardize on an overlay encapsulation
+protocol. It increases scalability up to 16 million logical networks and
+allows for layer 2 adjacency across IP networks. Multicast or unicast with
+head-end replication (HER) is used to flood broadcast, unknown unicast,
+and multicast (BUM) traffic.
+
+The VXLAN specification was originally created by VMware, Arista Networks
+and Cisco. Other backers of the VXLAN technology include Huawei, Broadcom,
+Citrix, Pica8, Big Switch Networks, Cumulus Networks, Dell EMC, Ericsson,
+Mellanox, FreeBSD, OpenBSD, Red Hat, Joyent, and Juniper Networks.
+
+VXLAN was officially documented by the IETF in :rfc:`7348`.
+
+If configuring VXLAN in a VyOS virtual machine, ensure that MAC spoofing
+(Hyper-V) or Forged Transmits (ESX) are permitted, otherwise forwarded frames
+may be blocked by the hypervisor.
+
+.. note:: As VyOS is based on Linux and there was no official IANA port assigned
+   for VXLAN, VyOS uses a default port of 8472. You can change the port on a
+   per VXLAN interface basis to get it working across multiple vendors.
+
+Configuration
+=============
+
+Common interface configuration
+------------------------------
+
+.. cmdinclude:: /_include/interface-common-without-dhcp.txt
+  :var0: vxlan
+  :var1: vxlan0
+
+VXLAN specific options
+-----------------------
+
+.. cfgcmd:: set interfaces vxlan <interface> vni <number>
+
+  Each VXLAN segment is identified through a 24-bit segment ID, termed the
+  :abbr:`VNI (VXLAN Network Identifier (or VXLAN Segment ID))`, This allows
+  up to 16M VXLAN segments to coexist within the same administrative domain.
+
+.. cfgcmd:: set interfaces vxlan <interface> port <port>
+
+  Configure port number of remote VXLAN endpoint.
+
+  .. note:: As VyOS is Linux based the default port used is not using 4789
+     as the default IANA-assigned destination UDP port number. Instead VyOS
+     uses the Linux default port of 8472.
+
+.. cfgcmd:: set interfaces vxlan <interface> source-address <interface>
+
+  Source IP address used for VXLAN underlay. This is mandatory when using VXLAN
+  via L2VPN/EVPN.
+
+Unicast
+^^^^^^^
+
+.. cfgcmd:: set interfaces vxlan <interface> remote <address>
+
+  IPv4/IPv6 remote address of the VXLAN tunnel. Alternative to multicast, the
+  remote IPv4/IPv6 address can set directly.
+
+Multicast
+^^^^^^^^^
+
+.. cfgcmd:: set interfaces vxlan <interface> source-interface <interface>
+
+  Interface used for VXLAN underlay. This is mandatory when using VXLAN via
+  a multicast network. VXLAN traffic will always enter and exit this interface.
+
+
+.. cfgcmd:: set interfaces vxlan <interface> group <address>
+
+  Multicast group address for VXLAN interface. VXLAN tunnels can be built
+  either via Multicast or via Unicast.
+
+  Both IPv4 and IPv6 multicast is possible.
+
+Multicast VXLAN
+===============
+
+Topology: PC4 - Leaf2 - Spine1 - Leaf3 - PC5
+
+PC4 has IP 10.0.0.4/24 and PC5 has IP 10.0.0.5/24, so they believe they are in
+the same broadcast domain.
+
+Let's assume PC4 on Leaf2 wants to ping PC5 on Leaf3. Instead of setting Leaf3
+as our remote end manually, Leaf2 encapsulates the packet into a UDP-packet and
+sends it to its designated multicast-address via Spine1. When Spine1 receives
+this packet it forwards it to all other Leafs who has joined the same
+multicast-group, in this case Leaf3. When Leaf3 receives the packet it forwards
+it, while at the same time learning that PC4 is reachable behind Leaf2, because
+the encapsulated packet had Leaf2's IP-address set as source IP.
+
+PC5 receives the ping echo, responds with an echo reply that Leaf3 receives and
+this time forwards to Leaf2's unicast address directly because it learned the
+location of PC4 above. When Leaf2 receives the echo reply from PC5 it sees that
+it came from Leaf3 and so remembers that PC5 is reachable via Leaf3.
+
+Thanks to this discovery, any subsequent traffic between PC4 and PC5 will not
+be using the multicast-address between the Leafs as they both know behind which
+Leaf the PCs are connected. This saves traffic as less multicast packets sent
+reduces the load on the network, which improves scalability when more Leafs are
+added.
+
+For optimal scalability Multicast shouldn't be used at all, but instead use BGP
+to signal all connected devices between leafs. Unfortunately, VyOS does not yet
+support this.
+
+Example
+-------
+
+The setup is this: Leaf2 - Spine1 - Leaf3
+
+Spine1 is a Cisco IOS router running version 15.4, Leaf2 and Leaf3 is each a
+VyOS router running 1.2.
+
+This topology was built using GNS3.
+
+Topology:
+
+.. code-block:: none
+
+  Spine1:
+  fa0/2 towards Leaf2, IP-address: 10.1.2.1/24
+  fa0/3 towards Leaf3, IP-address: 10.1.3.1/24
+
+  Leaf2:
+  Eth0 towards Spine1, IP-address: 10.1.2.2/24
+  Eth1 towards a vlan-aware switch
+
+  Leaf3:
+  Eth0 towards Spine1, IP-address 10.1.3.3/24
+  Eth1 towards a vlan-aware switch
+
+**Spine1 Configuration:**
+
+.. code-block:: none
+
+  conf t
+  ip multicast-routing
+  !
+  interface fastethernet0/2
+   ip address 10.1.2.1 255.255.255.0
+   ip pim sparse-dense-mode
+  !
+  interface fastethernet0/3
+   ip address 10.1.3.1 255.255.255.0
+   ip pim sparse-dense-mode
+  !
+  router ospf 1
+   network 10.0.0.0 0.255.255.255 area 0
+
+Multicast-routing is required for the leafs to forward traffic between each
+other in a more scalable way. This also requires PIM to be enabled towards the
+Leafs so that the Spine can learn what multicast groups each Leaf expect
+traffic from.
+
+**Leaf2 configuration:**
+
+.. code-block:: none
+
+  set interfaces ethernet eth0 address '10.1.2.2/24'
+  set protocols ospf area 0 network '10.0.0.0/8'
+
+  ! Our first vxlan interface
+  set interfaces bridge br241 address '172.16.241.1/24'
+  set interfaces bridge br241 member interface 'eth1.241'
+  set interfaces bridge br241 member interface 'vxlan241'
+
+  set interfaces vxlan vxlan241 group '239.0.0.241'
+  set interfaces vxlan vxlan241 source-interface 'eth0'
+  set interfaces vxlan vxlan241 vni '241'
+
+  ! Our seconds vxlan interface
+  set interfaces bridge br242 address '172.16.242.1/24'
+  set interfaces bridge br242 member interface 'eth1.242'
+  set interfaces bridge br242 member interface 'vxlan242'
+
+  set interfaces vxlan vxlan242 group '239.0.0.242'
+  set interfaces vxlan vxlan242 source-interface 'eth0'
+  set interfaces vxlan vxlan242 vni '242'
+
+**Leaf3 configuration:**
+
+.. code-block:: none
+
+  set interfaces ethernet eth0 address '10.1.3.3/24'
+  set protocols ospf area 0 network '10.0.0.0/8'
+
+  ! Our first vxlan interface
+  set interfaces bridge br241 address '172.16.241.1/24'
+  set interfaces bridge br241 member interface 'eth1.241'
+  set interfaces bridge br241 member interface 'vxlan241'
+
+  set interfaces vxlan vxlan241 group '239.0.0.241'
+  set interfaces vxlan vxlan241 source-interface 'eth0'
+  set interfaces vxlan vxlan241 vni '241'
+
+  ! Our seconds vxlan interface
+  set interfaces bridge br242 address '172.16.242.1/24'
+  set interfaces bridge br242 member interface 'eth1.242'
+  set interfaces bridge br242 member interface 'vxlan242'
+
+  set interfaces vxlan vxlan242 group '239.0.0.242'
+  set interfaces vxlan vxlan242 source-interface 'eth0'
+  set interfaces vxlan vxlan242 vni '242'
+
+As you can see, Leaf2 and Leaf3 configuration is almost identical. There are
+lots of commands above, I'll try to into more detail below, command
+descriptions are placed under the command boxes:
+
+.. code-block:: none
+
+  set interfaces bridge br241 address '172.16.241.1/24'
+
+This commands creates a bridge that is used to bind traffic on eth1 vlan 241
+with the vxlan241-interface. The IP-address is not required. It may however be
+used as a default gateway for each Leaf which allows devices on the vlan to
+reach other subnets. This requires that the subnets are redistributed by OSPF
+so that the Spine will learn how to reach it. To do this you need to change the
+OSPF network from '10.0.0.0/8' to '0.0.0.0/0' to allow 172.16/12-networks to be
+advertised.
+
+.. code-block:: none
+
+  set interfaces bridge br241 member interface 'eth1.241'
+  set interfaces bridge br241 member interface 'vxlan241'
+
+Binds eth1.241 and vxlan241 to each other by making them both member interfaces of
+the same bridge.
+
+.. code-block:: none
+
+  set interfaces vxlan vxlan241 group '239.0.0.241'
+
+The multicast-group used by all Leafs for this vlan extension. Has to be the
+same on all Leafs that has this interface.
+
+.. code-block:: none
+
+  set interfaces vxlan vxlan241 source-interface 'eth0'
+
+Sets the interface to listen for multicast packets on. Could be a loopback, not
+yet tested.
+
+.. code-block:: none
+
+  set interfaces vxlan vxlan241 vni '241'
+
+Sets the unique id for this vxlan-interface. Not sure how it correlates with
+multicast-address.
+
+.. code-block:: none
+
+  set interfaces vxlan vxlan241 port 12345
+
+The destination port used for creating a VXLAN interface in Linux defaults to
+its pre-standard value of 8472 to preserve backwards compatibility. A
+configuration directive to support a user-specified destination port to override
+that behavior is available using the above command.
+
+Unicast VXLAN
+=============
+
+Alternative to multicast, the remote IPv4 address of the VXLAN tunnel can be
+set directly. Let's change the Multicast example from above:
+
+.. code-block:: none
+
+  # leaf2 and leaf3
+  delete interfaces vxlan vxlan241 group '239.0.0.241'
+  delete interfaces vxlan vxlan241 source-interface 'eth0'
+
+  # leaf2
+  set interface vxlan vxlan241 remote 10.1.3.3
+
+  # leaf3
+  set interface vxlan vxlan241 remote 10.1.2.2
+
+The default port udp is set to 8472.
+It can be changed with ``set interface vxlan <vxlanN> port <port>``