vPC (Virtual port-channel )

Overview

A virtual PortChannel (vPC) allows links that are physically connected to two different Cisco Nexus 7000 or 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 7000 or 5000 Series Switches, but it can also be deployed along with Cisco Nexus 2000 Series Fabric Extenders.

The following list defines critical vPC concepts:

• vPC: vPC refers to the combined PortChannel between the vPC peer devices and the downstream device.

• vPC peer switch: The vPC peer switch is one of a pair of switches that are connected to the special PortChannel known as the vPC peer link. One device will be selected as the primary device, and the other will be the secondary device.

• vPC peer link: The vPC peer link is the link used to synchronize states between the vPC peer devices. The vPC peer link carries control traffic between two vPC switches and also multicast, broadcast data traffic. In some link failure scenarios, it also carries unicast traffic. You should have at least two 10 Gigabit Ethernet interfaces for peer links.

• vPC domain: This domain includes both vPC peer devices, the vPC peer keepalive link, and all the PortChannels in the vPC connected to the downstream devices. It is also associated with the configuration mode that you must use to assign vPC global parameters.

• vPC peer keepalive link: The peer keepalive link monitors the vitality of a vPC peer switch. The peer keepalive link sends periodic keepalive messages between vPC peer devices. The vPC peer keepalive link can be a management interface or switched virtual interface (SVI). No data or synchronization traffic moves over the vPC peer keepalive link; the only traffic on this link is a message that indicates that the originating switch is operating and running vPC.

• vPC member port: vPC member ports are interfaces that belong to the vPCs.

vPC configuration on the Cisco Nexus 5000 Series includes these steps:

• Enable the vPC feature.

• Create a vPC domain and enter vpc-domain mode.

• Configure the vPC peer keepalive link.

• (Optional) Configure system priority.

• (Optional) Configure vPC role priority.

• Create the vPC peer link.

• Move the PortChannel to vPC.