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New Member

Nexus 5000 peer-switch

We have a DC network comprising 2 x VSS clusters and 2 x Nexus 5020 VPC pairs.

The 5020 switches do not have "peer-switch" defined (i.e is seen as individual STP bridges).

To simplify and to make the solution more robust we are planning to configure "peer-switch" on all Nexus 5000 switches.

What kind of downtime can we calculate with when configuring this?

What actually happens when "peer-switch" is defined?

See attached drawing.

NxOS version 5.2.1.N1.6


Everyone's tags (5)

Nexus 5000 peer-switch


See this:

vPC Peer Switch

The vPC peer switch feature addresses performance concerns around STP convergence. This feature allows a pair of Cisco Nexus devices to appear as a single STP root in the Layer 2 topology. This feature eliminates the need to pin the STP root to the vPC primary switch and improves vPC convergence if the vPC primary switch fails.

To avoid loops, the vPC peer link is excluded from the STP computation. In vPC peer switch mode, STP BPDUs are sent from both vPC peer devices to avoid issues related to STP BPDU timeout on the downstream switches, which can cause traffic disruption.

This feature can be used with the pure peer switch topology in which the devices all belong to the vPC.


Peer-switch feature is supported on networks that use vPC and STP-based redundancy is not supported. If the vPC peer-link fail in a hybrid peer-switch configuration, you can lose traffic. In this scenario, the vPC peers use the same STP root ID as well same bridge ID. The access switch traffic is split in two with half going to the first vPC peer and the other half to the second vPC peer. With the peer link failed, there is no impact on north/south traffic but east-west traffic will be lost (black-holed).

It does not mention anything about downtime however it is highly recommended to do this during a maintenance window.

Hope this helps.

Hall of Fame Super Silver

Nexus 5000 peer-switch

Downtime should be very minimal but I agree with Leo - plan to do it during a maintenance window.

Note "peer switch" requires NX-OS 5.2(1)N1 or later. I see many shops with older 5k's not runing this recent of code revision.

New Member

Re: Nexus 5000 peer-switch

Thanks for info!
I will plan a maintenance window.

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