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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.

Dr-IP

The easiest way to do what you want to do is to turn on QOS, if not already on, and set the switchport priority on the ports used for video conferencing equipment to 7. With that done anything coming from the video conferencing gear should get higher priority over every thing else.

One thing I should note, is with all the routing being done only on the end switch, it creates a lot of extra traffic on its link, as every packet that needs to be routed, not local to the end switch, has to go all the way to the end switch, and then back to its destination. Besides being inefficient, if something goes wrong with the routing on that end switch, connectivity between all sites goes down.

What I would do is set each switch to do the routing for its local VLAN, and route any non local traffic directly to the correct switch, instead of out to the end, and back again. Also if the end switch were to die, at least the 3 other sites would still be able to communicate with each other.

interface FastEthernet0/1
switchport access vlan 5
switchport priority default 7

cisdoz2

ASKER

That is a good point and I had already given that some thought. The problem I had with that is that the video equipment will not work with NAT and must be assigned a public ip address. Is there a way to route across several routing switches to a single ip address that belongs to the same subnet as the first switch without doing the VLAN setup I created? I have provided a brief diagram:

Routed Switches
|---------------------------------------------------------|
Internet ----> Router ----> Switch1 ----> Switch2 ----> Switch3 ----> Switch4 ----> Video Conferencing Device
X.X.X.225 X.X.X.226
----------- -----------
255.255.255.224 255.255.255.224

I realize I could split my assigned public addresses into smaller subnets, but with so few, that is really not an option.

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Dr-IP

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cisdoz2

ASKER

Looks like a plan, Doc

Thanks