vPC Peer Switch Deployment Options

[Mohamed Anees Mohammed Abdulla]

• Introduction
• Prerequisites
• Related Information

Introduction

This document describes options for deployment of vPC Peer Switch. When a Virtual Port Channel (vPC) is configured and operational, the Spanning Tree Protocol (STP) continues running on both vPC peer devices. The vPC peer switch is introduced to address performance concerns around these STP convergence events.

Prerequisites

Familiarity and understanding of Nexus switches and Spanning tree protocol.

Related Information

Nexus 1000v Port-Channel Best Practices

[Dave Mumford]

Hi Anees,

Thanks for this doc , its very useful. I've been reading this in conjunction with vpc best practices

http://www.cisco.com/c/dam/en/us/td/docs/switches/datacenter/sw/design/vpc_design/vpc_best_practices_design_guide.pdf (Novenber 2015), the following section has got me thinking whether I should be using peer-switch (same SPT VLAN priorites) over not using peer-switch and having a primary and secondary root bridge configured on the N7K aggregation layer.

Section vPC and Spanning Tree Protocol Bridge Protocol Data Units

Strong Recommendations:
● Always define the vPC domain as STP root for all VLAN in that domain (configure aggregation vPC peer devices as STP root primary and STP root secondary)

General Recommendations:
● Configure the Spanning Tree Protocol root for all VLAN on vPC primary device (spanning-tree vlan 100-102 root primary)
● Configure the Spanning Tree Protocol secondary root for all VLAN on vPC secondary device (spanning-tree vlan 100-102 root secondary

therefore  Im still a bit unsure as to whether we should be configuring peer-switch as default best practice (and matching SPT vlan priorities) no matter whether we use a pure vpc or hybrid environment.

I think the answer is going to be yes but would like clarification on my understanding if possible to the following:

- in pure vpc environment like 2.1 topology peer-switch should be configured , this will allow for faster convergence of the STP topology when a failed N7K is restored, rather than configuring SPT root and secondary priorities on the N7K aggregation devices.

- peer-switch is only configured on the N7K aggregation layer and SPT vlan priorities MUST match on both the primary and secondary N7Ks.

- There is NO need to configure peer-switch on the access layer N5K's.

- In topology 2.1 , is there any need to configure STP vlan priorities  on the N5Ks or leave these to work themselves out.

Thanks in advance.

regards,

Dave.

[Patrick Colbeck]

I've been wondering much the same Dave. STP on the second layer of a vPC topology.