Here's a Scenario regarding Layer 2 VLAN

[MIBSWE]

Hi,

I'm a first timer to VLANs, but have reasonable knowledge about TCP/IP, subnetting etc. Here's a scenario that I have had a request on and I'm seeking the best way to achieve it.

We have a HP Procurve 1800-24G J9028B layer 2 switch. At the moment there are no VLANs set up. Everyone can access/see each other on the same subnet ie. 192.168.1.x. We have had problems where people have accessed our demo room devices (on same subnet) and interfered (by accident) a demo. So, we want to be able to have the ability to temporarily disconnect connectivity between the demo room devices and all other non demo devices, while still allowing everyone internet access via the router. But we only need this setup when a demo is ongoing. So, when the demo has finished, they can switch back to everyone being able to see each other via the network.

My first thought was to create two VLANs id 10 and id 20. The devices will still have the same IP addresses and subnet. So as an example:

VLAN 10 - Demo devices

port 2 - 192.168.1.10/24

port 3 - 192.168.1.11/24

port 4 - 192.168.1.12/24

VLAN 20 - Non Demo Devices

port 10 - 192.168.1.20/24

port 11 - 192.168.1.21/24

port 12 - 192.168.1.22/24

Router will be on port 1 acting as the gateway with 192.168.1.1 and will be a member of both VLANs 10 & 20, so everyone can get access to he internet regardless of which VLAN they are connected to.

I will have an 'old school' 2 port switch like this one in the demo room https://www.amazon.com/SANOXY-Network-Switch-Manual-Sharing/dp/B004Y34VQS?th=1. So one port will connect to VLAN 10 (when a demo is in progress) and the other to VLAN 20 (when the demo is finished). 

So first of al,l am I breaking any rules here with VLANs? Am I trying to do the impossible? It's not a usual situation from what I can see, so any suggestions on how to do this with the HP layer 2 switch would be great. 

Thanks in advance!