This Video Contains VXLAN Frame format and explanation of each field, as described in RFC7348. Video link: https://www.youtube.com/watch?v=rXhLB7FMIBI&feature=youtu.be

1. VXLAN
Encapsulation
and its Frame
Format
By Mohammed Umair

2. VXLAN Frame Format
 A Native/Original Ethernet frame will be
encapsulated with four Header.
 VXLAN Header is a 8 byte field that has
1) Flags (8 bits): I Flag is 1 bit, set to 1 for Valid
VNI, rest 7 bits are reserved
2) VXLAN Network Identifier: is a 24 bit value used
to designate the individual VXLAN overlay
network on which the communicating VMs are
situated.
3) Reserved fields (24 bit and 8 bit): must be set to
0

3. VXLAN Frame Format Contd…
 Outer UDP Header: Outer UDP Header with a Source
Port provided by the VTEP and the Destination Port
being a well known Port Assigned by IANA
1) Destination Port : IANA has assigned Destination Port
number 4789 for VXLAN
2) Source Port: It is recommended that the UDP Source
port be calculated using Hash of fields from the inner
packet. It is recommended that the value be in the
range between 49152-65535
3) UDP Checksum

4. VXLAN Frame Format Contd…
 Outer IP Header: Having Source IP and
Destination IP Address.
1) Source IP Address: Source IP Address indicates
the IP Address of the VTEP over which the
communicating VM is running or communicating
VM is connected to.
2) Destination IP Address: The Destination IP
Address can be Unicast or Multicast IP Address.
Unicast IP Address indicates the Destination
VTEP IP. Multicast IP is used when Multicast
routing is used for VXLAN Signaling.

5. VXLAN Frame Format Contd…
 Outer Ethernet Header
1) Outer Destination MAC Address: This
Address can be of Target VTEP or of an
intermediate Layer 3 router.
2) Outer Source MAC Address: This Address is
MAC address of the Tunnel Source VTEP.
3) Outer VLAN Tag is optional.

6. Outer Ethernet Header
Outer Destination MAC Address
Outer Destination MAC
Address
Outer Source MAC Address
Outer Source MAC Address
Optional Ethtype = C-TAG
802.1Q
Outer.VLAN Tag Information
Ethertype = 0x0800 (for IPV4)
Ethertype = 0x86DD (for IPV6)

7. Outer IPV4 Header
Version
Header
Length TOS Or DiffServ Total Length
Identifier FLAG
S
Fragment Offset
TTL Protocol=17(UDP) Header Checksum
Outer Source IPV4 Address
Outer Destination IPV4 Address

8. Outer IPV6 Header (if IPV6 is
used as underlay)
Version Traffic Class Flow Label
Payload Length NxtHdr=17(UDP) Hop Limit
Outer Source IPv6 Header
Outer Destination IPv6 Header

9. Outer UDP Header
Source Port Destination Port = VxLAN Port
UDP Length UDP Checksum

10. VXLAN Header
R R R R I R R R Reserved
VXLAN Network Identifier (VNI) Reserved

11. Inner (Native) Ethernet Header
Inner Destination MAC Address
Inner Destination MAC
Address
Inner Source MAC Address
Inner Source MAC Address
Optional Ethtype = C-TAG
802.1Q
Inner.VLAN Tag Information

12. Payload
Ethertype of Original Payload
Original Ethernet Payload (FCS of original Ethernet Frame
Not Included)

13. Frame Check Sequence
New FCS (Frame Check Sequence) for Outer Ethernet
Frame

14. Sample Frame with VxLAN
Header

15. Thank You