How many stacking cables do i need to physically stack two MS250-48FP-HW switches?

[JohnReed]

the SKU MA-CBL-40G-1M shows 2 ports on each end of the cable, which would tell me I would only use 1 stacking cable to connect 2 switches. is that correct?

[PhilipDAth]

Negative.  You need two cables to create a ring.

[JohnReed]

just to be clear...  QTY 2 of MA-CBL-40G-1M are necessary to stack 2 switches?

[PhilipDAth · Accepted solution]

Correct.  If the switches are going to be right next to each other you'll be able to use the shorter stacking cables such as MA-CBL-40G-50CM (this is assuming you are using a switch with 80Gb/s of stacking [aka 2 x 40Gb/s cables] like an MS225).

[JohnReed]

OK. thank you. the documentation and the visuals are rather lacking. it was hard enough to get a picture of the stacking cable.

I did mention the 50cm cable as an option to the customer but he wanted 1m just in case.

Per my subject line I am using the MS250-48FP-HW switches in this case.

thank you,

John

[PhilipDAth]

The MS250 also uses an 80Gb/s stacking connector so uses the same cables.

The cables are not that expensive compared to the switches.  I often include extra cables because of this.  Having an extra unused cable is much easier than having a cable too short and is unusable.

[PhilipDAth]

This is a good article about connecting up physical stacks.

https://documentation.meraki.com/MS/Stacking/Configuring_a_Physical_Switch_Stack

[JohnReed]

yes, I actually already looked at that and was part of what I was talking about documentation earlier.

It shows one line from one switch to the next. then a second line from the bottom switch to the top switch, implying two different cables; however, the SKU itself has 2 cables as part of the assembly, hence my confusion.  I did not find an actual picture of the back of the switch (not an architectural picture) that has the detail showing if each port is actually broken into two parts or not.

[msosa]

Hello, My question would be, if just have 2 switches, the "ring" stacking is mandatory?? I mean: could I just connect 1 cable to create the Stack?

[PhilipDAth]

If you want to stack them use two stacking cables.

Otherwise you could just connect then with an Ethernet cable.

[msosa]

thank you for your answer, but it is not the same, an ethernet cable would give me a 1Gbps link, while the stacking gives 40Gbps.. I know having two cables is the best, but I´d like to know if having only one could work? 

   Thank you again!

[PhilipDAth]

It would result in the stack being in a permanent broken state but it would work.

I wouldn't do it. You are asking for problems.

[msosa]

Understood! thank you @PhilipDAth

[watdee]

I also wasn't sure if I needed two cables for my stacks of two switches so I went with one cable and it works perfectly fine.  No errors in the dashboard or anything.  My stacks are of two MS225 and two MS250 switches.  I guess I should order the 2nd cable?

[cmr]

@watdee you may get errors if you reboot the stack, or you.may be lucky.  I'd definitely get a second cable!

[watdee]

My two, two switch stacks have been up for over a year after software upgrades and several reboots, still no issue in the dashboard.  I don't mind adding a second cable to the switches that have the dedicated stack ports on the back just to be safe though. 

However, I also have a pair of MS425-16 and if I use both the 40GB/s ports for stacking, then I lose the 40GB/S uplinks to my other building.

[watdee]

Just found some more info regarding other brands and stacking two switches with one cable.  It sounds like it works fine just isn't recommended for redundancy reasons.

https://networkengineering.stackexchange.com/questions/62651/how-many-stack-cables-would-be-needed-i...

https://community.extremenetworks.com/extremeswitching-other-233226/how-many-stack-cables-for-two-sw...

https://community.cisco.com/t5/routing/number-of-stack-cables-for-two-3650/td-p/3179794

I'll probably end up using two cables to be on the safe side.