virtual PortChannel, or vPC. Although a pair of switches acting as a vPC peer endpoint looks like a single logical entity to PortChannel-attached devices, the two devices that act as the logical PortChannel endpoint are still two separate devices. This environment combines the benefits of hardware redundancy with the benefits of PortChannel loop management. The other main benefit of migration to an all-PortChannel-based loop management mechanism is that link recovery is potentially much faster. Spanning Tree Protocol can recover from a link failure in approximately 6 seconds, while an all-PortChannel-based solution has the potential for failure recovery in less than a second.
Rich Hintz on 09 Jan 09technology tutorial describes how Cisco migrated its U.S. WAN from a hub-and-spoke network design that supported primarily client/server applications to a peer-to-peer network that supports advanced voice and video applications.