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Reference Virtual Chassis Fabric Topologies

This section provides three VCF reference topologies, and a summary of the pros and cons of each topology.


A VCF should include at least four members—two spine devices and at least two leaf devices. A three-member VCF is not a supported configuration. For topologies with three or fewer members, use a Virtual Chassis configuration instead.

Figure 1 shows the reference topologies.

Figure 1: Good and Bad Spine and Leaf ExamplesGood and Bad Spine and Leaf Examples

Example 1: If you want to build a VCF with two spine devices, we recommended that you use all 40-Gbps links, as shown in the first topology in Figure 1. In this topology, the multicast bandwidth for the VCF is 40 Gbps.

Example 2: If you want to build a VCF with 40-Gbps and 10-Gbps links between spine and leaf devices, we recommend that all 40-Gbps links are terminated on the same set of spine devices, and all 10-Gbps fabric links are also terminated on the same set of spines, as shown in the second topology in Figure 1. Note that in this scenario, bandwidth for leaf-to-leaf unicast traffic is 50 Gbps while the fabric bandwidth for multicast traffic is only 10 Gbps.

Example 3: We do not recommended mixing path bandwidth at a single spine, as show in the third topology in Figure 1. VCF still functions in these topologies, but performance is not optimal. These topologies should only be used as transient topologies and are not recommended for production networks.