why- Open BSD .rocks

vxlan(4) (∞)

The vxlan interface is a tunnelling pseudo-device for overlaying virtualized layer 2 networks over layer 3 networks.

A vxlan interface can be created using the ifconfig vxlanN create command. Once configured, the interface encapsulates and decapsulates Ethernet frames in UDP datagrams that are exchanged with tunnel endpoints. The default UDP port for VXLAN traffic is 4789.