The Nexus 7000 and 5000 series switches take port-channel functionality to the next level by allowing Muli-Chassis port aggregation. It was introduced in version 4.1(4).
Port-channels configured as vPC can only be used as L2 links and no dynamic routing protocol should be used across the link.
vPCs are configured by associating two Nexus devices into a vPC domain, the information is exchanged between peers across 2 links;
- vPC peer-keepalive link – heartbeat between peers to ensure both devices are online thus helping to avoid split-brain senario.
- vPC peer link – exchanges state information between the peers and provided additional mechanisms that help detect split-brain scenarios.
The following steps are used to configure vPC;
- Enable the vPC feature on each peer
- Create VRF for the VPC keepalive link
- Verify connectivity of the VPC peer keepalive link and its working
- Configure the vPC peer-link
- Verify configuration consistency checks and vPC is active
- Add port channels to a vPC and verify its operational
This feature is designed to enable certain storage, application servers or load balancers to implement fast-path functionality. This causes nodes to send return traffic to a specific MAC address of the sender rather than HSRP address. By default, this traffic might be dropped as VPC loop avoidance does not allow traffic received on a VPC peer-link to be forwarded out a VPC interface (loop avoidance). A VPC Peer-Gateway enables the VPC peer device to forward packets destined for its peer router MAC locally.