Question : Problem: QOS over VLAN

I have 3 3750 SMI and 1 3550 EMI switches connected in a straight line (daisy chained) across 4 sites.  Sites are connected with Gigabit SFPs using fiber.  The core routing switch is located at Site 1.  I have 1 VLAN at each site with the 3750 SMI doing inter-vlan routing at Site 1 for all the rest of the VLANs.

I want to add a second VLAN at Site 4 using QOS over that VLAN from Site 1, through Site 2 and Site 3 to Site 4.  The new VLAN will be used for Video Conferencing.

Can you tell me how to configure this for each site so that traffic destined for Video Conferencing is prioritized over all other traffic.

Answer : Problem: QOS over VLAN

Maybe you could create some kind of GRE tunnel, but that would be a real klutzily solution. The best way to do what you want to do is use trunks between the switches, and create a separate VLAN for the video traffic to go through.

If you plan your steps carefully, the impact on the network should be minimal. One hint, if you don’t have trunking between the switches yet, start enabling on the furthest switches link port first, and work your way back, and before issuing the trunk command for the port, always issue a reload in 2 command before on the far end switch first. That way if something goes wrong and you can't reestablish connectivity on the far switch after setting the links on booth switches to trunking, the far end switch will reboot reloading the old config allowing you to reestablish a connection to it.

This is a handy trick by the way, as it has allowed me to safely do some very extensive network reconfiguring on remote equipment thousands of miles away from where I work. That I would have never dared to do unless I have a technician standing by at the remote site.