No Link Connectivity to half of my 4 Cohesity Nodes via SFP DAC cables - No connectivity!

[ktv-meraki]

Hi Community,

I have a frustrating issue at on offsite data center:  Did a firmware upgrade on my switches from 17.1.3 to 17.2.1.1 and after the reboot my Cohesity cluster has two nodes that are not getting link.  I've tried rolling back the firmware and then when that didnt work I reinstated it.  Called Meraki support and they recommended we go on site, try other cables and swap them around.  I have a handful of these cables and not a single one worked.  I did however get link when I connected the non-working nodes to the two SFP ports that were up. That of course led me back to the switch.  I have 8 available ports on two different switches and non will accept the connection.  What gives!  I also overnighted two new DAC cables from FS with luck.  Meraki of course is recommending their approved cables via the documentation.  Anyone else have these challenges.  They have been working for 2 years, and I have 4 working with no issues at another datacenter.  Cohesity does not care what cables you use.  In fact, they have no guidelines telling you what to use.  I spent two hours on a call with them, and they said t was nothing on their hosts.

I would greatly appreciate some guidance.  Is the next step to buy Meraki certified SFP modules?  They don't exactly have recommended DAC cables.  I would love to know if others have had issues like this with Meraki switches.

Here are the cables we have:

Amazon.com: 10Gtek 10G SFP+ DAC Cable - 10GBASE-CU Passive Direct Attach Copper Twinax SFP Cable for...

FS:

https://www.fs.com/products/30862.html?attribute=8722&id=2354432

[Mloraditch]

I’ve not worked with Cohesity but the only way Meraki support will help further is with the official Meraki parts.

Now one thing I might try is a factory reset of the switches. You said it happened after a firmware update but the rollback didn’t help. It could be the config is messed up locally and a reset will clear it. Rare but Ive seen it happen 

[cmr]

@ktv-meraki there are Meraki SFP+ DAC cables, this one is the equivalent of your Amazon one: MA-CBL-TA-3M | Meraki Twinax Cable

I'd get one of those, even if it just to rule the cable out of being the problem.

[PhilipDAth]

If I understand correctly; some nodes are down and some nodes are up and working?

When you compare a down and up node - what is the difference between them?  Do tey have different DAC cable manufacturers?

If you hover over the Meraki switch port - does it identify a DAC as being plugged in (even if down)?  How does that compare to a working node?

[ktv-meraki]

Correct, 2 nodes of the 4 nodes on the back of this cohesity cluster are down.  All 4 nodes are part of the same pizza box of a server.  All 4 nodes were using the same DAC from the same manufacturer. 

Hovering over the ports just say disconnected.  The switch is recognizing the module as I scroll down to status.  

I do have a switch at this site that hasn't been used yet.  I could fire that one up and see if I can get connectivity to rule out the 3 switches in this network.

The thing that keeps pointing me to Meraki is that plugging node 3 and 4 into a known working host port brought them up.

[PhilipDAth]

Is this a switch stack, or standalone switches?

What model switch?  E,g. MS350-24X.

[ktv-meraki]

MS225-24

Not stacked

[ktv-meraki]

Just wanted to update. Meraki replaced our switch after many different tests pointed to failed ports.  Thanks for your input!