VXLAN – Virtual Extensible Local Area Networks
What is VXLAN?
- Virtual Extensible LAN (VXLAN) is a network virtualization technology that addresses the scalability problems across data center networks.
- VXLAN is an L2 overlay over an L3 network. It uses a VLAN-like encapsulation technique to encapsulate MAC-based OSI layer 2 Ethernet frames within layer 3 UDP packets.
- Each overlay network is known as a VXLAN Segment and identified by a unique 24-bit segment ID called a VXLAN Network Identifier (VNI).
- Only virtual machines on the same VNI are allowed to communicate with each other. Virtual machines are identified uniquely by the combination of their MAC addresses and VNI.
- The VXLAN technology is created by Cisco, VMware , Citrix and RedHat.
Why VXLAN is required?
VXLAN technology is developed to address the below problems which are frequently encountered in the Data Center & in the Cloud computing network.
Limitation of 4094 broadcast domains -VLAN
- Limitations of the no of the VLANs supported in the network. The no of VLAN supported on the traditional network is 4094.
- Most of the could service providers faces the VLAN short comings since multi companies & multi tenants requires unique VLAN ID & the segmentation of each company resources will lead to utilization of the VLANs. Scalability is an issue.
- VXLAN address this problem by increasing traditional VLAN limits from 4094 to 16 million.
- It uses a 24-bit segment identifier to scale beyond the 4096 limitations of VLANs.
Layer 2 extensions across Data Center & Mobility
VXLAN address the Layer 2 extensions between different data center sites that must share the same logical networks.
- Extending Layer 2 domains across Layer 3 network is not possible. This means the same VLAN cannot be extended beyond the Layer 3.
- VXLAN technology addresses this by binding the two separate layer 2 domains and makes them look like one.
- VXLAN supports the long distance V-motion & High Availability (HA) across data center.
- VXLAN also address the problem of scalability by expanding the L2 network across datacenter & maintaining the same network.
- It does not depend on STP to converge the topology. Instead Layer 3 routing protocols are used.
- No links within the fabric are blocked. All links are active and can carry traffic
- The fabric can load balance traffic across all active links, ensuring no bandwidth is sitting idle.
VXLAN Use Cases – Summary
- Cloud Service Providers or Data Center which requires more than 4096 VLAN for network segmentation.
- Stretching Layer 2 domains across the data center in order to accommodate growth without breaking the Layer 2 adjacency requirement for the services & applications.