Figure 126. Example of VLT DeploymentVLT on Core SwitchesUplinks from servers to the access layer and from access layer to the aggregation layer are bundled inLAG groups with end-to-end Layer 2 multipathing. This set up requires “horizontal” stacking at the accesslayer and VLT at the aggregation layer such that all the uplinks from servers to access and access toaggregation are in Active-Active Load Sharing mode. This example provides the highest form ofresiliency, scaling, and load balancing in data center switching networks.The following example shows stacking at the access, VLT in aggregation, and Layer 3 at the core.The aggregation layer is mostly in the L2/L3 switching/routing layer. For better resiliency in theaggregation, Dell Networking recommends running the internal gateway protocol (IGP) on the VLTi VLANto synchronize the L3 routing table across the two nodes on a VLT system.Enhanced VLTAn enhanced VLT (eVLT) configuration creates a port channel between two VLT domains by allowing twodifferent VLT domains, using different VLT domain ID numbers, connected by a standard link aggregationcontrol protocol (LACP) LAG to form a loop-free Layer 2 topology in the aggregation layer.This configuration supports a maximum of four switches, increasing the number of available ports andallowing for dual redundancy of the VLT. The following example shows how the core/aggregation portdensity in the Layer 2 topology is increased using eVLT. For inter-VLAN routing and other Layer 3 routing,you need a separate Layer 3 router.Virtual Link Trunking (VLT) 925
