VXLAN Tutorial

As networks — especially large provider and data center networks — grew in size and relied more heavily on virtualization, the limitations of traditional VLANs became hard to ignore. VXLAN (Virtual Extensible LAN) was developed specifically to address these limitations.

Limitations of Traditional VLANs

• Limited ID space — a VLAN ID is only 12 bits long, which caps the total number of VLANs at 4,096. For a large provider serving many customers, or a large enterprise, this ceiling is reached surprisingly quickly.
• Spanning Tree blocking redundant links — to prevent loops, STP blocks any redundant path, which means capacity that has already been paid for simply sits unused.
• MAC address table load — with widespread virtualization, a single physical switch port may need to support many different virtual machines, each with its own MAC address, putting a heavy learning burden on distribution-layer switches.
• Constrained VM mobility — live migration of a virtual machine generally requires the VM to stay within the same subnet, which limits how freely workloads can move around a data center.

What VXLAN Is