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● VLAN: It is optional in a VXLAN implementation and will be designated by an ethertype of 0×8100 and
has an associated VLAN ID tag.
● Ethertype: It is set to 0×0800 because the payload packet is an IPv4 packet. The initial VXLAN draft
does not include an IPv6 implementation, but it is planned for the next draft.
Outer IP Header: The Outer IP Header consists of the following components:
● Protocol: It is set to 0×11 to indicate that the frame contains a UDP packet .
● Source IP: It is the IP address of originating VTEP.
● Destination IP: : It is the IP address of target VTEP.
Outer UDP
Header:
The Outer UDP Header consists of the following components:
● Source Port: Entropy of the inner frame. The entropy could be based on the Inner L2 header or Inner
L3 header.
● VXLAN Port : IANA-assigned VXLAN Port (4789).
● UDP Checksum: The UDP checksum field is transmitted as zero. When a packet is received with a
UDP checksum of zero, it is accepted for decapsulation.
VXLAN Header :
● VXLAN Flags : Reserved bits set to zero except bit 3, the first bit, which is set to 1 for a valid VNI
● VNI: The 24-bit field that is the VXLAN Network Identifier
● Reserved: A set of fields, 24 bits and 8 bits, that are reserved and set to zero .
Frame Check
Sequence (FCS):
Note that the original Ethernet frame's FCS is not included, but new FCS is generated on the outer
Ethernet frame.
Limitations on VXLAN
While configuring a VXLAN, the following conditions apply:
● Hybrid ports are not supported in VXLAN (hybrid port means an interface tagged to one VLAN and untagged to another
VLAN).
● The show vxlan vxlan-instance statistics remote-vtep-ip and the show vxlan vxlan-instance
statistics instance commands are not supported in a NSX environment.
● VXLAN is not supported in a stacking setup.
● VXLAN with VRF configuration is not supported.
● Routing over VXLAN is not supported in a controller-based VXLAN setup.
● SNMP and REST API are not supported for VXLAN configurations.
● Multicast over VXLAN is not supported.
● In multicast and broadcast traffic, even though the remote VTEP is reachable through the ECMP path, load balancing is not
supported.
●
Only one Remote VTEP can be reached through a single interface in a broadcast domain.
● Single VNI can be mapped to Single VLAN in both static and NSX controller-based VXLAN. Hence, only 4000 VNIs are
supported while configuring static VXLAN.
● You can map multiple VNIs with multiple VLANs in an NSX-based VXLAN.
● You can configure only one Nuage controller in a VXLAN setup. Nuage controller datapath-learning is not supported.
● In a Nuage controller-based VXLAN deployment, station moves of non-virtualized entities may not work as expected due to a
possible issue in the Nuage contoller.
NOTE:
When more than 15000 learned MAC addresses are synchronized from the Nuage controller to one of the VTEPs,
the SSL connection between the controller and the VTEP flaps continuously.
Virtual Extensible LAN (VXLAN) 1021