VXLAN packet format

A VTEP encapsulates a frame in the following headers:

  • 8-byte VXLAN header: VXLAN information for the frame.
    • 24-bit VXLAN ID: Identifies the VXLAN of the frame. It is also called the virtual network identifier (VNI).

    • Flags: If the I bit is 1, the VXLAN ID is valid. If the I bit is 0, the VXLAN ID is invalid. All other bits are reserved and set to 0.

  • 8-byte outer UDP header for VXLAN: The default VXLAN destination UDP port number is 4789.

  • 20-byte outer IP header: Valid addresses of VTEPs or VXLAN multicast groups on the transport network. Devices in the transport network forward VXLAN packets based on the outer IP header.