A topology group is a named set of VLANs and bridge-domains that share a Layer 2 control protocol. Topology groups simplify configuration and enhance scalability of Layer 2 protocols by allowing you to run a single instance of a Layer 2 protocol on multiple VLANs and bridge-domains. One instance of the Layer 2 protocol controls all the VLANs and bridge-domains.
You can use topology groups with the following Layer 2 protocols: