How to replace a stacked switch (24-port with a 48-port) ?

[DualWeaponWord]

Hi,

I'm looking for some advice regards the correct process to follow with regards to replacing a 24-port switch belonging to a stack, with a new 48-port switch. The purpose being to increase the number of ports available in the stack.

Below are the switch/stack details:

Mbr
ID   |  Mac Address     |  Model                                                    |  Pri   | Status
1     |  5820b1-fda980   |  HP J9729A 2920-48G-POE+ Switch  |  128  |  Member
2     |  3ca82a-58f2c0   |  HP J9727A 2920-24G-PoE+ Switch    |  128  |  Commander
3     |  b05ada-3295c0  |  HP J9728A 2920-48G Switch             |  128  |  Member
4    |  b05ada-32d5c0  |  HP J9728A 2920-48G Switch              |  128  |  Standby

The above stack is then connected to stack 2 (which contains 3 switches) via 10GB Module (J9732A).

I'm not sure what happened for the 24-port switch to take on the Commander role but it shoud be the Standby with the fiirst 48-port switch (Mbr ID : 1) holding the Commander role. Guessing it's down to the order they were initially booted with as they all share the same default priority.

The software on installed on the new switch is the same as the software installed on the stack (WB.16.03.0005).

I've also inserted a new stacking module into the rear of the new 48-port switch so that stacking is enabled without having to manually enable it.

I know that then I remove the Commander switch from the stack, the current Standby switch will become the new Commander and then one of the member switches will be elected as new Standby. I'm also aware that if I was to remove the 24-port switch and replace it with a like-for-like switch, the configuration will be unaffected but as this isn't a like-for-like replacement I'm not sure what will happen to the configuration on the stack if when I insert the new switch into the stack?

How will the config be affected when I remove the 24-port switch? I have a backup of the config saved onto USB so will it be a case of importing this and making adjustments as needed?

Any help is much appreciated, thank you.

[parnassus]

Hello,

First thing first: if you are going to replace the 24 ports with a 48 ports (moving to another SKU - AKA Product Number Jxxxxx - of the same Aruba 2920 family) you're going to lose the configuration regarding those 24 ports...configuration for those 24 ports will not be retained [*]...so be prepared to redefine/reconfigure their configuration once the new 48 ports member will become part of the stack (plus configuring the remaining twenty four ports that are new entries).

The one thing I see is that Stack Members priorities are wrong because are set all to the same value (128)...the Master role election was probably won by the Switch having the MAC Address with the lower value (there are other election rules that should have kicked in...generally the priority is the most important value to decide who will be the Commander and who the Standby...well the sentence should be "Other rules in the election process can override this priority."): you should try first to fix the Stack Member priorities otherwise the Commander removal requires you to execute a redudancy switchover so the Commander role will be passed to the Standby stack member...if you are going to fix the roles first then the switch that you want to exchange will own the Member role or, at worst, the Standby role...not the more important Commander role (which, you want the Switch Id 1 to have...if I've read you correctly on the Forum post).

There is a nice HP 2920 Stacking Technical Whitepaper which can guide you to fix stack member ID and/or priorities and to manage a stack member removal and provision (addition). See here.

Then there is the whole Chapter 9 of the Aruba 2920 Advanced Traffic Management Guide for ArubaOS-Switch 16.08 (here) that explain how to manage an Aruba 2920 Stack.

Finally I suggest you - at the end of your substitution procedure - to upgrade from ArubaOS-Switch 16.03 to latest ArubaOS-Switch 16.08 so you will be in a safer position with regards to stack-related bugfixes and features.

Hope the suggestions above will help you to perform a flawless transition to a full stack of 48 ports Switches...in any case we're here to help!

[*] See here for the part of configuration retention/deletion.