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Cisco datacenter: vPC Features and purpose

Today we are going to talk about the vPC feature with the benefit and the overview of that feature. As we know that vPC is a virtualization technology that presents paired or two Nexus devices as a unique Layer 2 logical node to the access layer devices or endpoints. vPC belongs to Multichassis EtherChannel family of technology.

What is vPC in Datacenter?
A virtual port channel (vPC) allows links that are physically connected to two different Cisco Nexus 7000 or 5000 Series devices to appear as a single port channel to a third device. The third device can be a switch, server, firewall, load balancer or any other networking device that supports link aggregation technology.

Using vPC we will have operational and architectural advantages:

  • Simplifies network design
  • Build highly resilient and robust Layer 2 network
  • Enables seamless virtual machine mobility and server high-availability clusters
  • Scales available Layer 2 bandwidth, increasing bisectional bandwidth
  • Grows the size of the Layer 2 network
  • vPC feature is included in the base NX-OS software license 

vPC provides the following technical benefits:

  • Eliminates Spanning Tree Protocol (STP) blocked ports
  • Uses all available uplink bandwidth; Layer 2 hashing algorithm
  • Allows dual-homed servers to operate in active-active mode
  • Provides fast convergence upon link or device failure
  • Offers dual active/active FHRP (default gateways) for servers.
  • Each peer device in the vPC domain runs its own control plane, and both devices work independently
let's talk about some of the features we are using in the datacenter while operating with the vPC environment.

vPC auto-recovery : Provides a backup mechanism in case vPC peer-link failure followed by vPC primary peer device failure. It also provides a back when ever both vPC peer device reload or power outage and only one vPC peer comes up. The feature allows one vPC device to assume STP/vPC primary role and bring up all local vPCs.

vPC Peer-Gateway: Allows a vPC switch to act as the active gateway for packets addressed to the peer router MAC.

vPC Orphan-ports suspend: When vPC peer links go down, vPC secondary shuts down all the vPC member ports as well as orphan ports. It avoids single attached devices like firewall, load balancers or NIC teamed devices when isolated during vPC peer link failure.

vPC ARP SYNC: Improve convergence for layer 3 flows after vPC peer-link is up or recovers from a failure.

vPC peer-Switch: Virtualize both vPC peer devices so they appear as a unique STP root bridge.

vPC role & System Priority: Manually set vPC system priority to ensure vPC peer devices are the primary devices on LACP and also manually set the vPC role as primary and secondary.

vPC Delay restore: Delays vPC member links from bring up on the recovery vPC peer device. This allows for the layer 3 routing protocols to converge before allowing any traffic on vPC member links. It results in graceful restore and zero packet loss during the recovery phase. This feature is enabled by default and the time is 30 seconds


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