MS350 - Connect Second Stacking Cable

[NSN]

Two MS350-24 in a stack but with only one stacking cable.  We were going to order the second cable and connect it. Opened a case with support to verify this could be done while the switches are on like a Cisco Catalyst but they said connecting stacking cables while the switches are powered on can cause unexpected behavior.

Has anyone ever connected the second stacking cable while the switches were operational and know the results?

[DarrenOC]

Hi @NSN , it’s Merakis best practice to build the stack whilst powered down. It’s noted in their documentation.  To that end we’ve always built our stacks whilst they’ve been powered down.

I wouldn’t venture off the beaten track

[NSN]

I tend to agree but this site is 24x7 and want to avoid taking an outage if someone has experience doing this live.  Just wanted to check with the community since I don't have the equipment to lab this up.

[DarrenOC]

@cmr  - don’t suppose you tried this with your MS355’s?

[cmr]

We found that connecting a first (or second) stacking cable between MS355s when powered on lit up the ports but didn't transfer any data.  However on MS225s and MS210s they seemed to connect up properly first time...

[PhilipDAth]

Never tried it.  But in theory, you are taking an existing already built stack in a "failed" state (because it is missing a cable), and adding a cable that will bring it back out of the "failed" state.

I think it should work.  I'd do it at an off-peak time.

[KarstenI]

I also suspect that it should work based on the "Failed" state as mentioned by @PhilipDAth.

I would assume (but I don't know and have not tested it) that the following procedure will further reduce the likelihood of problems:

1. Power off one of the switches. With all systems connected redundantly there should not be any outage.
2. Connect the second Stack-cable
3. Power on the the switch.

Here it should behave pretty much the same as if a stack-member gets restarted.

[NSN]

@KarstenI that isn't a bad idea.  Could at least keep the redundantly connected systems up.  

[RaymondH]

I was in the same situation, I did not have long enough cable from the first to the last, but stack was established anyhow to get everything online fast.

Can confirm it worked without problems with that method on MS210 switches. (First tried to just connect the cable "hot", but that made some of the switches go offline, not good...)