vPC

[Sahil-Khan-Pathan]

Can somebody please explain me the vpc concept.

[Joseph W. Doherty]

Are you familiar with Etherchannel?

If so, one of the restrictions of Etherchannel, each side needs to be one physical device.

With the advent of stackable switches or VSS or virtual stackable switches, the one physical device can be multiple physical devices that runs as one logical device.

vPC (on Nexus) further extends Etherchannel to a pair of physical devices, that continue to operate as a pair of distinct physical devices yet support Etherchannel by making it behave as if it was working with just one physical device.

Much more information should be obtainable by searching either the Internet or Cisco's main site.

[M02@rt37]

Hello @Sahil-Khan-Pathan 

vPC for Virtual Port Channel is a cisco Nexus feature (NX-OS) that let you connect one device (like a server or switch) to 2 nexus switches using 1 logical port channel, while both switches stay active...

It provides link and device redundancy without blocking any links (unlike spanning tree). The two nexus switch sync control info over a special vPC peer link, so they act as one logical switch toward connected devices...

https://blog.avidpontoon.co.uk/cisco-nexus-vpc-part-1-concepts-and-initial-setup/

[Joseph W. Doherty]

Just to embellish M02@rt37 's reply, to avoid misunderstanding some of his statements. . .

. . . to 2 nexus switches using 1 logical port channel, while both switches stay active. . .

By "active", what's meant, each vPC Nexus switch remains a distinct device.  With the stackable/VSS implementations, members are all data active but logically there's but one logical device.  The logical device is controlled by an individual physical stack member which may be called the "active" switch, which it is for the logical device.

It provides link and device redundancy without blocking any links (unlike spanning tree).

Physical device redundancy is also provided by the stackable approach.  Etherchannel being considered just a single link is a feature of it, regardless of its underlying hardware.

Oh also (I believe), some Etherchannel implementations support defining member links in excess of how many can actually be active carrying traffic.  Such excess links can take the place of a failed activity data carrying link.

[balaji.bandi]

suggest start reading this :

https://www.cisco.com/c/dam/en/us/td/docs/switches/datacenter/sw/design/vpc_design/vpc_best_practices_design_guide.pdf

[tinil]

vPC is a simply a way to make two separate Nexus switches to look like one switch to anything that connects to them(with a portchannel). Normally, an EtherChannel must come from one physical switch. With vPC, two Nexus switches coordinate with each other so a device can form an EtherChannel that spans both switches at the same time.

The switches stay independent. there is a vPC Peer-Link and vPC Keepalive for the communication between the switches. Hence vPC gives you multi-homing with full redundancy, while still keeping both Nexus switches independent.