VPC on Fexs N2K-C2248TP-E-1-GE towards 3850 switches

[Garry Kabbay]

Hi Experts

I have scenario where I have Fex 111 only connected on 9K1 and Fex 112 only connected on 9K2. and the Fex model of both Fexs are N2K-C2248TP-E-1-GE. 

If I want to make VPC from 9k fexs to 3850 S1 and 3850 S2, is it possible ? because I only saw the example which showing the VPC with Servers not with switch.

or I should make simple port-channel like 9k1 fex 111 to 3850 S1 and 9k2 fex 112 to 3850 S2 ?

Topology : this is I am trying to Achieve as I see lot of example with servers, but nothing with switches (3850)

Please guide.

Regards

Gary

[MHM Cisco World]

If you meaning one vpc to two SW' then you can not do that.

You need one vpc from both NSK to one SW

MHM

[Garry Kabbay]

actually due to racks physical location means distance between 9ks rack and 3850s Rack : I cannot make direct connectivity. Only I am having Fexs near to these 3850 switches.

So you are saying from Fexs it is not possible to make VPC with other 3850 switches ?

[Garry Kabbay]

this is the topology for your reference, which I am trying to make and looking for feasibility

[Pavel Tarakanov · Accepted solution]

https://www.cisco.com/c/en/us/support/docs/switches/nexus-2000-series-fabric-extenders/200363-nexus-2000-fabric-extenders-supported-un.html#anc15

https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus9000/sw/93x/fex/configuration/guide/b-cisco-nexus-2000-nx-os-fabric-extender-configuration-guide-for-nexus-9000-switches-93x/b-cisco-nexus-2000-nx-os-fabric-extender-configuration-guide-f...

It's achievable but from 3850 you need to enable bpfu filter, otherwise FEX will put ports to err-disable.

Also, please check links above.

[Elliot Dierksen]

I don't think you can do that. There are limits on what you can do with a FEX. My understanding is that they are intended only for endpoints, not for links to other switches.

[Garry Kabbay]

Thanks Pavel, Elliot and MHM for your expert advice,

So avoiding this complexity of enable bpdu filter , limitation of Fexs etc : Should I use simple port channel from Fexs to 3850 switches ?  will the port-channel option be simple and ok for this Scenario ?

Kindly guide.

Regards

Gary

[Elliot Dierksen]

I assume the downlink to the FEX's are fiber. Is that correct? Do you have any extra pairs available? Anything you do with the FEX to use it as a link to another switch is not using the device as it was intended/designed. At least that is my understanding. I am suggesting that you find a way to doing the switch to switch link without using the FEX because then you can achieve the VPC redundancy you want without introducing any odd issues that can be a pain to support.

[Garry Kabbay]

Hi Elliot

This is 1-G copper (N2K-C2248TP-E-1-GE) Fexs and I have to connect the 3850 switches with this copper 1 G Fexs only. So shall i make port channel from these Fexs instead of VPC ?

Regards

Gary