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Before deploying the VxRail cluster, configure the Enterprise SONiC fabric with the VxRail networks required by the VxRail cluster, as described in VxRail cluster deployment.
In multirack deployments, these VxRail Infrastructure VLANs need to be stretched across the fabric racks where the single VxRail cluster has been deployed, as shown in Figure 5.
The multirack environment leverages BGP EVPN VXLAN to stretch the networks. To do this, virtual tunnels are deployed using the Enterprise SONiC EVPN VXLAN feature.
A virtual extensible LAN (VXLAN) extends L2 host connectivity, such as virtual and physical machines in tenant segments, over an underlying L3 transport network in a multitenant, virtualized data center. The overlay (Virtual Extensible LAN) VXLAN networks, as shown in the following figure, use VTEPs for the encapsulation and decapsulation of VXLAN packets. Each VTEP is associated with a Network Virtual Interface (NVE) loopback interface.
This loopback interface is the tunnel source IP address. UDP headers use this address to specify the source and destination addresses of hosts that send or receive VXLAN encapsulated packets.
The packets that are destined to a remote device are sent to the local VTEP as the first hop. The packet is encapsulated with a VXLAN header that includes the VNI with VLAN and the IP mapping of the destination host, as shown in the following figure. The packet is sent to the destination VTEP. The destination VTEP extracts the original packet and routes it to the destination.
There are two types of VTEPs, physical and logical. The physical VTEP is created between two physical end points or interfaces, whereas the endpoints of the logical VTEP are based on a logical construct.
As shown in Figure 4, a logical VTEP is created between the leaf switch pairs. The leaf switch pairs are configured to act as a single logical device for all VXLAN tunnel end points.
The logical VTEP forms a BGP EVPN VXLAN session with the remote leaf switch pair, and each remote leaf forms a single VXLAN tunnel with the logical VTEP.