H3C Technologies H3C S12500-X Series Switches - Manual (Page 8)

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VXLAN overview
Virtual eXtensible LAN (VXLAN) is a MAC-in-UDP technology that provides Layer 2 connectivity between
distant network sites across an IP network. VXLAN is typically used in data centers for multitenant
services.
VXLAN provides the following benefits:
• Support for more virtual switched domains than VLANs—Each VXLAN is uniquely identified by a
24-bit VXLAN ID. The total number of VXLANs can reach 16777216 (2
24 ). This specification makes
VXLAN a better choice than 802.1Q VLAN to isolate traffic for VMs.
• Easy deployment and maintenance—VXLAN requires deployment only on the edge devices of the
transport network. Devices in the transport network perform typical Layer 3 forwarding.
The device supports only IPv4-based VXLAN. IPv6-based VXLAN is not supported.
Hardware compatibility
Only FX and FC cards support VXLANs.
FC cards cannot provide VXLAN IP gateway services.
An FX card cannot connect to a user site if it acts as a centralized VXLAN IP gateway.
VXLAN network model
As shown in Figure 1 , the transport edge devices assign VMs to different VXLANs, and then forward
traffic between sites for VMs by using VXLAN tunnels.
The transport edge devices are VXLAN tunnel endpoints (VTEP). They can be servers that host VMs or
independent network devices.
An H3C VTEP uses VSIs and VXLAN tunnels to provide VXLAN services.
• VSI—A virtual switching instance is a virtual Layer 2 switched domain. Each VSI provides switching
services only for one VXLAN. VSIs learn MAC addresses and forward frames independently of one
another. VMs in different sites have Layer 2 connectivity if they are in the same VXLAN.
• VXLAN tunnel—Logical point-to-point tunnels between VTEPs over the transport network. Each
VXLAN tunnel can trunk multiple VXLANs.
VTEPs encapsulate VXLAN traffic in the VXLAN, outer UDP, and outer IP headers. The devices in the
transport network forward VXLAN traffic only based on the outer IP header.