Our office is set in two different floors. Both floors have managed switches, with a single ethernet wire connecting them. Here are some bullets of what I have on each floor:
1st floor
- Firewall
- Switch A (48 port)
- Server A
- ISP Modem 1
- ISP Modem 2
- ISP Modem 3
2nd floor
- Switch B (24 port)
- Server B
The firewall is acting as my DHCP server. The subnet I'm using is 192.168.0.0/24.
ISP Modem 3 is usually connected to Server A (in the same floor). I need to temporarily connect it to Server B, which is in the 2nd floor instead, and I can't easily route a secondary cable for this between the floors.
Can I use VLANs for this? I tried the following:
- I picked port 25 of Switch A and configured it with VLAN 9 (tagged).
- I picked port 21 of Switch B and configured it with VLAN 9 (tagged).
- On the upstream ports (Switch A port 49, and Switch B port 25) I added VLAN 9 tagged.
I did not change anything on the ISP Modem (I can't) nor on the Server B (I think I don't need to). I assumed this simple VLAN setup would act as a simple wire across the floors.
Am I correct with my assumptions? I'm asking, of course, because I don't seem to have connectivity between Server B and ISP Modem 3 as I expected.
You can, and should, use VLANs for this, but you need to make the "access ports" (the ports you plug the equipment into) "untagged" on VLAN 9 (or whatever), because those devices think they're just plugging into a regular switch port, and don't (and shouldn't) know anything about the VLAN tagging going on.
For the trunk ports (the inter-switch links) you have correctly configured those to pass the VLAN traffic "tagged", so that the switches know that the relevant packets are associated with the specific VLAN, and they can forward them appropriately.