Introduction to VXLAN: Virtual extensible Local Area network

Today I am going to talk about the basics about VXLAN as many of you asked about the same. VXLAN stands for Virtual extensible Local Area network. VXLAN is an open-standards solution that extends Layer 2 bridge domains across a shared Layer 3 infrastructure. Essentially an overlay technology positioned to overcome several disadvantages of traditional Layer 2 networks.

With overlays, the original packet or frame is packaged or encapsulated at a source edge device with an outer header and dispatched toward an appropriate destination edge device.

Why VXLAN?

Scalability: VXLAN uses a 24-bit (16mil) network identifier as opposed to the traditional12-bit (4K) identifier.

Openness: VXLAN is an open-standard solution adopted by numerous venders, including Juniper, Arista, VMware, etc.

Elasticity: Allows for the addition of network capacity without impacting existing application workflows.Mobility, ECMP, Segmentation, etc.

Fig 1.1- VXLAN between sites

What is the various terminology used in VXLAN?

VNI/VNID: Virtual Network Identifier or VXLAN Network Identifier

Layer2 VNI carried in VXLAN bridged packets. VNI is configured per VLAN.

Layer3 VNI carried in VXLAN routed packets across VTEPs. One L3 VNI per tenant (VRF) Note: Tenant, VRF, L3VNI are sometimes used interchangeably

VTEP: VXLAN Tunnel End Point

Performs VXLAN encapsulation/decapsulation

Could be hardware or software

NVE: Network Virtualization Edge

Logical representation of the VTEP

The tunnel interface (i.e. –MAC table shows NVE is the egress interface)

VXLAN Gateway

Device that forwards traffic between VXLANs

Can be both Layer 2 and Layer 3 forwarding.

Anycast Gateway

All VTEPs are configured with the same IP and MAC on a host facing SVI

Underlay Network: Provides the transport for VXLAN

IGP Routing (EIGRP, OSPF, ISIS)

Multicast Routing (PIM)

BGP Routing