VPC Terminology & Deployment Scenarios

VPC Terminology & Deployment Scenarios

Virtual Port Channel (vPC):

Virtual Port channel enables physical link to be connected to two different nexus 7000/5000 series switches to appear as a single port-channel to third device like switch, server, etc.

Following are the benefits of the vPC:

• It allow all ports of the STP to be in forwarding state, no blocked ports.
• Utilizes full available uplink bandwidth
• Does fast convergence when link or device fails.
• Provide active – active default gateways for end servers
• Provides Dual homed connectivity to servers.

 Below figure provide the physical and logical topology of the vPC.

End devices are connected to peer switch via vPC which uses all port-channel member link to forward traffic based on hash algorithms.

NX-OS Version & License requirement for vPC:

• For vPC to run on Nexus 7000 series switches, the NX-OS version must be equal or greater then NX-OS 4.1.3.
• For License, vPC runs on Base license of Nexus 7000/5000 series model.

Component of vPC:

Let’s discuss the component of vPC one by one and later we will see how to configure the vPC in steps:

• vPC Peer Device: A nexus 7000/5000 series switch which are used to create vPC domain and configure vPC.
• vPC Domain: Maximum Two Nexus devices are used to form vPC domain which makes the virtual MAC same for both peer device.
• vPC Peer-Link: A port-channel configure with peer-link command helps us to synchronize the control plane and CFS protocol. This link is also a Layer 2 trunk link for carrying vPC VLAN.
• vPC Peer-Keepalive Link: This is L3 link used to send vPC keepalive message every second to prevent the dual active or split brain scenarios.
• vPC Member Port: Those ports which are connected to end device or server and are part of port-channel and a particular vPC is said to be vPC member ports.
• vPC VLAN: Those VLAN which are allowed on vPC peer-link is called as vPC VLAN.

vPC Data Plane Loop Avoidance:

In vPC the loop is avoided at data plane rather than control plane. As per Cisco Design of vPC all data should be forwarded locally and peer-link should not be typically used for data packets. This is because Peer-link is used to synchronize control plane information like MAC address, Port-state information and IGMP information between peer-switch.