[c-nsp] Some basic vPC questions (nexus 3000)

Tim Stevenson tstevens at cisco.com
Fri Feb 7 12:06:53 EST 2014

Hi Drew, please see inline below:

At 07:50 AM 2/7/2014  Friday, Drew Weaver remarked:
>We are purchasing two Nexus 3000 switches to aggregate some 48 port 
>1G switches and plan on using vPC for redundancy.
>When I was reading the vPC whitepaper (referenced above) for the 
>Nexus 3000 it mentions two different types of vPC link:
>#1 The vPC peer keepalive link (whitepaper suggests that this 
>traffic can run over the mgmt. interface)
>#2 The vPC peer link (needs to be at least two 10G ports in a port channel)
>My questions are
>        What happens to the traffic if the vPC peer keep alive 
> communication fails between the two vPC members?

Nothing. You are of course alerted to that fact, but loss of 
bidirectional PKA communication does not impact data plane forwarding.

>        Depending on the answer to the question above, is it 
> possible to make the vPC peer keepalive link redundant?

You can, yes, it can be a port-channel for example.

>       Can you add more members to the vPC peer link port channel 
> without disrupting traffic flow?

There is potential for some disruption when you add/remove links from 
a port-channel, as hash buckets are shuffled around.

>        Has anyone run into any unexpected caveats or amusing issues 
> with vPC that they would like to share?

I yield the floor... ;)

Hope that helps,

>Thanks and happy Friday!
>cisco-nsp mailing list  cisco-nsp at puck.nether.net
>archive at http://puck.nether.net/pipermail/cisco-nsp/

Tim Stevenson, tstevens at cisco.com
Routing & Switching CCIE #5561
Distinguished Technical Marketing Engineer, Cisco Nexus 7000
Cisco - http://www.cisco.com
IP Phone: 408-526-6759
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