Downtime when removing or adding a switch to a stack ?

[thomasthomsen]

Is there any downtime (and if so, how long) if you add a new switch to a stack.

Example.

I have a couple of MS425 in a stack, and want to add another MS425 to that stack.

I would of course prepare the new MS425, adding it to the network, and getting it online (for firmware), and configure the stack ports on it, and perhaps already here add it to the stack ?

The current two switches are of course connected with two cables, so I would just take out one (cable), so that the current two are still operational with just one stacking cable between them, and then set in the new switch and recreate the ring.

What would happen, how much downtime would that give, if any, on the current running switches ?

And then of, course the other way around.

If I have to take one switch out. I would just suppose to power off the switch, remove it from the stackconfig, and physically remove it, and reconnect the stack in a ring.

What would the downtime be on the running switches ? (supposing of course that the switch I remove is not the "Active" one).

I cant really seem to find any information about this.

Do anyone know ?

Thanks

Thomas

[alemabrahao]

Take a look at this discussion.

https://community.meraki.com/t5/Switching/Remove-A-Stack-Member/m-p/194104#M13577

[thomasthomsen]

Well .. from that post , this does not boost confidence : "If you just want to remove the stack member and not replace it, I'm not sure if there's a process but I've seen instances where people have had to rebuild the stack entirely.".

Adding, however, from the post seems to be "ok".

But it would be nice is someone really knew.

[alemabrahao]

Any chance to perform a lab?

[thomasthomsen]

Sorry I don't have THAT many MS425's (or other stackable switches) in a lab 🙂 (Are you listening here @Meraki ... 🙂 ).

[JacekJ]

From my experience, adding or removing switches to a Meraki stack never caused a reboot, which you would get with classic Cisco Catalyst switches, BUT, if you are passing the magic 2 switches in a stack, things will get weird, here is a known issue:

Connecting a stacking cable to a stack that is online may result in a stack member going offline (present since MS 12)

If you connect a stacking cable in a at least 3 member stack you might notice one of the switches going offline (I would say I got that 75% of the cases, so each time I do this I assume this will happen). Most of the time, disconnecting and reconnecting a stacking cable helps, but sometimes this will fix one switch (bring it online), but break another (going offline).

This is really a guessing game, so if the switches are very crucial and you can spare a max 5min downtime, then just try connecting them, if one goes offline, power cycle them all at once and you will be good..

If you are adding only a 2nd switch and creating a 2 switch stack, you can play with everything running as long as the config is alright (I know, not recommended by Cisco, but that is my experience).

[thomasthomsen]

I think I have experienced something similar to that.

I have assumed it was a bug, that I thought was fixed.

Oh well.

[JacekJ]

You can say this one out loud, it's been around for way too long.

[PhilipDAth]

I would plan for a 30-minute outage.  I would personally reboot the whole stack after making a change like this to ensure stability.

[thomasthomsen]

Of course not the answer I was hoping for. 🙂

But I guess the, lets call it, ehhh,  "wildly different" experiences, and answers, goes to show that the documentation might be lacking a bit.