VPC is a Cisco Nexus terminology used to elevate the port-channel functionality to the next level. In VPC the links connected to two separate physical devices can be bundled together to form an ether-channel. Nexus family of switches supporting this technology are 9K, 7K, 5K and 3K.
There are various components of the VPC and below diagram illustrates most of them –
VPC Peer: These are the two Nexus devices which are interconnected via the VPC peer link. One serves the purpose of primary and other acts as Secondary.
VPC Peer link: It is the most important connectivity element between VPC peers. This link is used by the two VPC peers to synchronize their Control planes so that two switches have illusion of a single control plane. VPC link also carries the data traffic for Multicast, broadcast, unknown unicast and traffic of orphaned ports. VPC peer link is also used to determine if the remote peer is up and operational.
VPC PEER KEEPALIVE LINK: VPC peer keep alive link provides a layer 3 link between the two VPC peers which serves as secondary mechanism to check status of the remote peer. It helps the VPC switch to determine whether the peer link itself has failed or whether the VPC peer is down. This link doesn’t carry any synchronization data, it only sends keep alive IP/UDP packets on port 3200. Default timer for sending keep alive are 1 second and timeout of 5 seconds.
VPC MEMBER PORT: Port on VPC peer configured as member of any VPC.
ORPHAN DEVICE: Device that is on VPC VLAN but only connected to one VPC peer.SW1 in the diagram depicts the orphan device.
ORPHAN PORT: Port on the VPC peer where an Orphan device connects.
NON-VPC VLAN: Any of the STP VLANs not carried over the peer-link.
VPC DOMAIN: This is the common domain configured on two VPC peer devices and this value identifies the VPC. A VPC domain id per device is permitted.