VXLAN allows layer 2 segments to span layer 3 networks by encapsulating Ethernet frames within UDP packets. This allows virtual machines and servers to communicate securely across physical networks as if they were on the same local area network. VXLAN uses VXLAN Tunnel End Points and a VXLAN Network Identifier to encapsulate packets and identify virtual network segments. Up to 16 million virtual networks can be created, enabling data center tenants and workloads to be isolated from each other while residing on the same physical network.

1. Topic: Virtual eXtensible LAN(VXLAN)
By Math Tea – eintellego Networks
math@eintellegonetworks.asia
Date: 30 March, 2016

2. Contents
q VXLAN Introduction
q VXLAN Benefits
q Reference

3. What is VXLAN?
q Virtual eXtensible Local Area Network
q Stretches Layer 2 connections over a Layer 3 network by
encapsulating Ethernet frames in a VXLAN packet that
includes IP addresses
Layer 3 Network
Layer 2 over Layer 3Layer 2 Layer 2
VTEP-A VTEP-BHost 1 Host 2
VNI 6000

4. q Theoretically create as many as 16 million
VXLANs in an administrative domain
q Enable migration of virtual machines between
servers in separate Layer 2 domains by tunneling
over Layer 3 networks
q No need to use STP to converge the topology
u All links can be used
u Traffic can be load balanced
u Maximizes performance
Benefits of using VXLANs

5. VXLAN Network Identifier(VNI)
q The VNI was designed to address the growing needs of
multi-tenant data centers.
q VNI is 24 bit length which is more than 16 million
VXLAN segments(224 =16,777,216)

6. Virtual Tunnel Endpoint(VTEP)
q Devices that support VXLANs are called virtual tunnel
endpoints (VTEPs). They can be end hosts or network
switches or routers.
q VTEPs encapsulate VXLAN traffic and decapsulate that
traffic when it leaves the VXLAN tunnel.

7. q VTEPs add a numberof fields, including the following:
u Outer MAC destination address (MAC address of the tunnel endpoint
VTEP)
u Outer MAC source address (MAC address of the tunnel source VTEP)
u Outer IP destination address (IP address of the tunnel endpoint VTEP)
u Outer IP source address (IP address of the tunnel source VTEP)
u Outer UDP header
u A VXLAN header that includes a 24-bit field
Virtual Tunnel Endpoint(VTEP)

8. VXLAN Packet format
• LSRs forward packets based on label and swap labels:
- The last LSR in the path also removes the label
and forward the IP packets as normal IP Routing

9. Underlay Network

10. VXLAN Encapsulation
VNI =100
VNI =200
VNI =100
VNI =200

11. Overlay Network

12. Reference
• https://tools.ietf.org/html/rfc7348
• http://www.juniper.net/documentation/en_US/junos14.1/to
pics/topic-map/vxlan-qfx-series.html
• https://www.youtube.com/watchv=Jqm_4TMmQz8