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New Member

Nexus 7K and UCS connectivity


I'm new to UCS, so would appreciate some guidance on connecting a Fabric Interconnect cluster to a pair of N7K's. I understand the benefits of running in end host mode, but need to confirm what the best routing solution for the UCS VLANS would be.

Is it recommended to use a single vPC between the FI and pair of N7K's, running HSRP on each VLAN or use a pair of vPC's across each?

I'd heard that when running HSRP on uplink Switches, you should consider running the FI in switching mode.

Thanks in advance,


  • Unified Computing

Paul,Running the Fabric


Running the Fabric Interconnects in End Host Mode (EHM) is best, that way UCS uplinks are not blocked by STP as they would if you place the Fabrics in Switching Mode.

In the past, we used to recommend customer to run Switching mode for some specific behaviors EHM was not able to handle, but with the newer codes, 2.0 and on, EHM is enough unless you like STP and blocked ports (let's say you are too used to think about STP and its limitations that you don't want to change to EHM).

The way traffic will be sent to the upstream switch depends on the way you pin the virtual interfaces of your server to the uplink ports, there is dynamic pinning (where UCSM decides where uplink port your traffic will travel through) and static pinning (where you can decide what link will be used)

Here you have some good documents for reference in regards to vPC and (this case) UCS:


This might also help you:

Using a single vPC is also supported and helpful, unless you have specific reasons to do it the way  you explained.

My 2 cents...



New Member

Thanks for the post and

Thanks for the post and information Kenny.

So in EHM mode, there should be no issues of running HSRP from the N7K's on each VLAN which is across both FI's or just one of them.


I don't see a problem in

I don't see a problem in running HSRP for each SVI...




A separate vPC from each FI

A separate vPC from each FI to both N7k!

as Kenny said, Ethernet switching mode is history; EHM is state of the art.

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