A virtual PortChannel (vPC) allows links that are physically connected to two different Cisco Nexus 5000 Series devices to appear as a single PortChannel to a third device. The third device can be a Cisco Nexus 2000 Series Fabric Extender or a switch, server, or any other networking device. A vPC can provide Layer 2 multipathing, which allows you to create redundancy by increasing bandwidth, enabling multiple parallel paths between nodes and load-balancing traffic where alternative paths exist.
After you enable the vPC function, you create a peer keepalive link, which sends heartbeat messages between the two vPC peer devices.
The vPC domain includes both vPC peer devices, the vPC peer keepalive link, the vPC peer link, and all the PortChannels in the vPC domain connected to the downstream device. You can have only one vPC domain ID on each device.
A vPC provides the following benefits:
• Allows a single device to use a PortChannel across two upstream devices
• Eliminates Spanning Tree Protocol blocked ports
• Provides a loop-free topology
• Uses all available uplink bandwidth
• Provides fast convergence if either the link or a device fails
• Provides link-level resiliency
• Helps ensure high availability
The vPC not only allows you to create a PortChannel from a switch or server that is dual-homed to a pair of Cisco Nexus 5000 Series Switches, but it can also be deployed along with Cisco Nexus 2000 Series Fabric Extenders. The deployment scenario in Figure 1 creates a vPC between the two ports on each of two Cisco fabric extenders.