VXLAN Hypervisor It is the VTEP that connects the Virtual Machines (VM) to the underlay legacy network to the physicalinfrastructure.Service Node(SN) It is also another VTEP, but it is fully managed by NSX. The purpose of SN is to be the central replication engine forflooded packetsLegacy TOR It is a TOR switch, which performs routing or switching decisions.Functional Overview of VXLAN GatewayThe following section is the functional overview of VXLAN Gateway:1 Provides connectivity between a Virtual server infrastructure and a Physical server infrastructure.2 Provides the functions performed by a VTEP in a virtual server infrastructure. The functions of a VTEP are:• VTEP is responsible for creating one or more logical networks.• VTEP is responsible for identifying and binding a Port and VLAN to a logical network• VTEP maintains MAC bindings to a VTEP.• VTEP is typically managed by a network orchestrator. When the device functions as VTEP, VXLAN from VMWare is the networkorchestrator.• VXLAN communicates with the VTEP using a standard protocol called OvsDb Protocol. The protocol uses the JSON RPC-basedmessage format.• The VTEP acts according to the TOR schema defined by VMWare. The solution is very specific to VMWare-based orchestrationplatforms and does not work with other orchestration platforms.VXLAN Frame FormatVXLAN provides a mechanism to extend an L2 network over an L3 network. In short, VXLAN is an L2 overlay scheme over an L3 networkand this overlay is termed as a VXLAN segment. VMs within the same VXLAN segment communicate with each other through a 24–bit IDcalled VXLAN Network Identifier (VNI). This 24–bit ID allows up to 16 million VXLAN segments to coexist within the same administrativedomain. The VNI scopes the inner MAC frame originated by the VM. This model has over-lapping MAC addresses without traffic cross-overVXLAN achieves L2 over L3 overlay using the tunneling mechanism. VTEPs are the end points of a tunnel located within the hypervisor onthe server that hosts VMs. The VXLAN frame format is shown in the following figure:Figure 151. VXLAN Frame FormatVirtual Extensible LAN (VXLAN) 1055
