Network virtualisation technology that addresses the scalability problems associated with traditional VLANs in large cloud computing deployments.
Encapsulation
VXLAN works by encapsulating Ethernet Frames within UDP Packets, allowing you to create virtual Layer 2 networks on top of Layer 3 infrastructure.
This creates logical networks that can span across physical network boundaries.
UDP is used for efficiency since VXLAN often is implemented in controlled environments like data centres where package loss is unlikely.
VXLAN Network Identifier (VNI)
Each VXLAN segment is identified by a 24-bit VNI, allowing for up to 16 million virtual networks (compared to just 4,096 with traditional VLANs using 12-bit VLAN IDs).
Tunnel Endpoints (VTEPs)
These are the devices that perform the encapsulation and de-encapsulation of packets. VTEPs map end devices to VXLAN segments and perform the actual encapsulation/de-encapsulation of traffic.
MAC Adress Learning
Similar to traditional switches, VXLAN learns MAC addresses but with the added complexity of mapping them to remote VTEPs.
Packet Structure
A VXLAN packet adds 50 bytes of overhead:
- 8 bytes for the VXLAN header (including the VNI)
- 8 bytes for the UDP header
- 20 bytes for the IP header
- 14 bytes for the outer Ethernet header