VXLAN network model
As shown in Figure 1, a VXLAN is a virtual Layer 2 network (known as the overlay network) built on top of an existing physical Layer 3 network (known as the underlay network). The overlay network encapsulates inter-site Layer 2 frames into VXLAN packets and forwards the packets to the destination along the Layer 3 forwarding paths provided by the underlay network. The underlay network is transparent to tenants, and geographically dispersed sites of a tenant are merged into a Layer 2 network.
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 HPE VTEP uses VSIs and VXLAN tunnels to provide VXLAN services.
VSI—A virtual switch 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.
Figure 1: VXLAN network model
