25Gb iSCSI Nexus 93180YC-EX and Dell Compellent SC5020

[dhabets-pqcorp]

Hi everyone,

I was hoping to find some advice or thoughts on an issue we've been experiencing with our newly purchased Cisco Nexus 9000 series switches and Dell Compellent SC5020.
We have a new Dell Compellent SC5020 equipped with 2 "Chelsio T6225 Dual Port 25Gb iSCSI Adapters" and 2x Nexus 93180YC-EX switches with Cisco SFP-10/25G-CSR-S transceivers. I am not able to establish a link between these devices however.

I checked the basics; I can see that a laserlight is being emitted on both ends, I can loop two of the same SFPs to establish a link - ie. the transceivers work with the fiber cables I am using (MM OM4). 

I have tried setting the link speed to 25Gb on the switch side, I have disabled FEC, changed the duplexing options, but all to no avail until now. 
My switches are on NX-OS 9.2(3).

Does anyone have a similar setup and managed to get it working? Am I missing something or am I lucky enough to have stumbled upon an interoperability issue..?

I have attached a sample of my interface configuration to show what I have right now.

I have opened a TAC case with Cisco on this, but that hasn't helped me much so far. Cisco states the issue is not with the Nexus switch or configuration.
Sadly though, the link works immediately when we're using a Dell switch we got on loan (but I definitely don't want to use Dell switching). Dell tells us exactly the same as Cisco does - the issue isn't on their side. Long story short, I am stuck between 2 parties.

Interesting to mention: I happen to have 10Gb transceivers for another Dell device that work in the Compellent - if I plug these in and set the interfaces on the Nexus switches to 10Gb the links establish. For the time being, I am using these.. but obviously this isn't the solution we want.

Any help or advice would be greatly appreciated.

Thanks and regards,
Dennis

[dhabets-pqcorp]

For anyone coming across this same issue, we have been able to resolve this using Cisco DAC cables between the Compellent and Cisco Nexus switches.

Be sure to turn off FEC for the interfaces the Compellent attaches to if the cable lenghts are below 2.5m. 

Dell has confirmed this setup to be approved and supported by them. 

The cables we used are: Cisco SFP-25G-CU1M

[lholder@osisoft.com]

Thanks for sharing this information I found it very helpful!

[luis.jorge]

I have exactly the same scenario. Has anyone been able to connect the SC5020 to the Nexus at 25G with SFPs?

So far I've only been capable of connecting the SC5020 with 10G SFPs...

[dhabets-pqcorp]

Hello Luis,

Sorry for the late reply - I didn't see your message.

We have got it working on 25GB using Cisco's DAC cables. You may want to get SFP-H25G-CU1M (or other length) DAC cables. 

Thanks and regards,
Dennis