Which of the following statements best describes vPC domains?
- There can be only two peers per domain.
- They monitor the status of vPC peers.
- They synchronize the state between two vPC peers.
- They synchronize the control plane and the data plane.
There can be only two peers, or switches, per virtual port channel (vPC) domain. A vPC enables you to bundle ports from two peers, which form a domain, into a single Open Systems Interconnection (OSI) Layer 2 port channel. Similar to a normal port channel, a vPC bundles multiple switch ports into a single high-speed trunk port. A single vPC domain cannot contain ports from more than two switches. For ports on two switches to successfully form a vPC domain, all the following must be true:
– The vPC feature must be enabled on both switches.
– The vPC domain ID must be the same on both switches.
– The peer keepalive link must be configured and must be 10 gigabits per second (Gbps) or more.
– The vPC number must be the same on both switches.
A vPC peer link, not a vPC domain, synchronizes the state between two vPC peers. A vPC peer link is typically comprised of a port channel made up of two physical ports on each switch. This link synchronizes Media Access Control (MAC) address tables between switches and serves as a transport for data plane traffic. Bridge protocol data unit (BPDU) and Link Aggregation Control Protocol (LACP) packets are also forwarded to the second peer over this link, which causes the vPC peers to appear to be a single control plane.
A vPC peer keepalive link, not a vPC domain, monitors the status of vPC peers. The peer keepalive link operates at Layer 3 of the OSI networking model; it is used to ensure that vPC switches are capable of determining whether a vPC domain peer has failed. Peer keepalive links can be configured to operate in any virtual routing and forwarding (VRF) instance, including the management VRF. Each vPC peer keepalive link is configured with the remote peer’s IP address as its destination IP address and the local peer’s IP address as its source address. Peer keepalive links must be trunk links.
Cisco Fabric Services, not a vPC domain, synchronizes the control plane and the data plane. Cisco Fabric Services is a messaging protocol that operates between vPC peers. Control plane and data plane information is synchronized over the vPC peer link.