M4300 12x12f no vlans while stacking failover

Hi MasterPhil

Welcome to the Community!

Let me first understand your setup, by explaining its reference design. A stack of two M4300-12X12F is a great redundant "core switch" for small to midsize networks. Let's speak about 'left' switch and 'right' switch, should those two half-width M4300 10G switches are horizontally stacked and occupying same U in your rack:

Say the left switch is the Master management unit. In case of failure,  the right switch will instantly take over as new Master management unit in the stack. So far he was the Backup management unit. With NSF (nonstop failover) there is no service interruption across this stack, including all LACP (distributed ling aggregation) links across both switches from rest of the network. This would imply your S3300 switches under the M4300 core stack should connect to both left and right switches using LACP connections (so dynamic LAGs). This way, no North-South service interruption for your access layer switches, should left or right switch at the core failover and failback again. Can you make sure you have LAGs properly configured on the core stack, and on your S3300 switches dual-homed to the core as well:

• On Fully Managed switches like M4300, LAGs are dynamic (LACP) by default
• On Smart Managed switches like S3300, LAGs are static by default, please enable Dynamic/LACP mode manually

Now, your VLAN issue. Thank you for reporting it. It shouldn't be any in case of failover (whole point of such High Availability installation). I can tell you this use case is heavily tested by us, and litterally by thousands of M4300 delighted customers, a few quarters only into its launch!

Let's understand the root cause of your VLAN discrepancy on the right switch. First of all, the right switch is active even when it's only the backup management unit, with the left switch up and running as Master management unit. In reading your explanations, I was under the impression you weren't sure of that. Of course we can test and remove power cord from left switch, in order to trigger accidental failover to right switch in terms of management, etc... but again, right switch is functional during normal stack operation. Moreover, the right switch configuration shouldn't change at all during the failover.

Why? Because there's only one configuration file for your entire stack. If you are using the Web GUI, you can open this configuration file by going Maintenance --> Export --> HTTP File Export and choose Text configuration in the drop menu:

Please do so and look at your Port VLAN configuration: say the left switch port and the right switch you are sequentially connecting your PC to.

• If this is the Port 15 on left switch, the port is called 1/0/15, meaning Unit=1 / Physical interface(so 0) / Port=15
• If this is the Port 15 on right switch, the port is called 2/0/15, meaning Unit=2 / Physical interface(so 0) / Port=15

If the VLAN behavior isn't the same between 1/0/15 and 2/0/15, it means the VLAN configuration isn't the same between 1/0/15 and 2/0/15. Again there's no configuration change during failover and failback: the configuration file is unique on both switches. Last, you don't need to force the failover from left switch to right switch, before testing your PC connection between 1/0/15 and 2/0/15. With the left switch up and running as Master management unit, please test your PC connected to 1/0/15, and then disconnect from left switch and connect your PC to right switch, port 2/0/15. If VLAN doesn't work, it means your configuration on 2/0/15 is the issue.

Can you control this? The Community will be happy to assist you further, please report the result.

Regards,