In a cloud environment, physical servers might be located in different Layer 2 networks. For example, a cloud might span physical servers that are in different geographical locations. In such cases, creating virtual machines (VMs) or tenants over a Layer 2 network restricts the number of physical servers that you can use for provisioning these VMs. You can use physical servers in different Layer 2 networks for provisioning VMs. However, as the migration between different servers is restricted to the same Layer 2 network, the utilization of the physical resource is not optimized.
VXLAN is a Layer 2 technology that enables you to create a Layer 2 network on top of a Layer 3 network, thereby providing further network isolation. VXLAN provides a virtual Layer 2 network that stretches over multiple physical Layer 2 networks. Therefore, provisioning resources in a cloud environment is not restricted to a single physical Layer 2 network. Physical servers can be a part of a VXLAN network as long as they are connected by IPv4 or IPv6 networks.
You can use the VXLAN technology with the Elastic Virtual Switch (EVS) feature of Oracle Solaris to create a large number of virtual networks. For information about how to use VXLAN with the EVS feature to create a virtual network, see Use Case: Configuring an Elastic Virtual Switch for a Tenant. For more information, see Chapter 5, About Elastic Virtual Switches and Chapter 6, Administering Elastic Virtual Switches.
VXLAN provides isolated Layer 2 segment that is identified by the VXLAN segment ID or VXLAN network identifier (VNI). All VMs in the same VXLAN segment belong to the same virtual Layer 2 broadcast domain.
Communication in VXLANs is similar to that in isolated VLANs. Hence, only VMs that are in the same VXLAN segment can talk to each other. VMs that are not in the same VXLAN segment cannot communicate with each other.