Stacking query

[Hudson1980]

I currently have a pair of 2920 switches in a ring stack, both switches have two 10gb modules in the back.

I wish to extend this stack from two to four switches.

I have read the stacking guidance and its left me unclear as to whether i have to shutdown my entire core network or not.

from one point of view it says to simply add the new switches in with the modules pre installed and the stack will extend itself automatically, would this suggest that i can simply break the stack and add in one switch, wait for the config to copy and then break it again and add the fourth switch.  all the while my core network stays intact albeit degraded.

The other view is that I have to switch off the entire stack, add in switch three, power up confirm that the config has copied, shutdown again and then add in switch four. 

Is anyone able to shed any light on this.

Thanks.

[Vince-Whirlwind]

You don't have to break the stack to add the new member, just break the ring.

So you currently have 

Switch1
 |   |
Switch2

Break the ring so you have:

Switch1
  |
Switch2

This has no effect on the network or switch operations.

Then tell the stack you are adding member 3:
stacking member 3 type <switch model J number> mac-address <mac address>

Then add your switch3:

Switch1
  |
Switch2
  |
Switch3

After you've got it to join the stack, add your next switch:

stacking member 4 type <switch model J number> mac-address <mac address>

Switch1
  |
Switch2
  |
Switch3
  |
Switch4

After you've got switch4 joined, close your ring again.

|-----Switch1
|       |
|     Switch2
|       |
|     Switch3
|       |
|-----Switch4

[Hudson1980]

 Thank you for clarifying things. 

Reading the documentation further it tells me that if i add a switch (via the stacking cable)  that has had the stacking module installed before first power on it will automatically add itself to the stack.

Does this follow on form what you mentioned before, or should i simply add it via the CLI?

Thanks again.