Dell C1048P Port Extender Networking Configuration Guide for the C9000 Series - Page 1066

Figure 139. Example of VLT Deployment VLT on Core Switches You can also deploy VLT on core switches. Uplinks from servers to the access layer and from access layer to the aggregation layer are bundled in LAG groups with end-to-end Layer 2 multipathing. This set up requires "horizontal" stacking at the access layer and VLT at the aggregation layer such that all the uplinks from servers to access and access to aggregation are in Active-Active Load Sharing mode. This example provides the highest form of resiliency, 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 the aggregation, Dell Networking recommends running the internal gateway protocol (IGP) on the VLTi VLAN to synchronize the L3 routing table across the two nodes on a VLT system. VLT Terminology The following are key VLT terms. • Virtual link trunk (VLT) - The combined port channel between an attached device and the VLT peer switches. • VLT backup link - The backup link monitors the vitality of VLT peer switches. The backup link sends configurable, periodic keep alive messages between the VLT peer switches. • VLT interconnect (VLTi) - The link used to synchronize states between the VLT peer switches. Both ends must be on 10G or 40G interfaces. 1066 Virtual Link Trunking (VLT)