Is it possible to base QOS on VLAN alone?

If the VLAN for that deparment has a certain IP subnet associated with it, you can use layer 3 QoS to give priority to traffic to and from that subnet.

At layer 2, you can define a QoS policy that prioritizes frames that arrive on the ports assigned to that particular VLAN.

I don't know what it means but we have:

interface GigabitEthernet3/7 ... qos vlan-based ...

It means that the physical port GE3/7 will use the layer 3 policy define for the vlan interface that GE3/7 is in.

For example

interface GigabitEthernet3/7 switchport access vlan 2 qos vlan-based . . interface vlan 2 service-policy output Policy10

Packets exiting GE3/7 will be classified and queued according to the policy Policy10.

Note that QoS at layer 3 (CBFWQ) only helps at times off congestion, and even PQ at gig speeds is fairly useless. Are you ports dropping packets on egress due to congestion ?

I think you should be looking at 'marking DSCP' at the edge, so the egress queing applied to the bottle necks or lower speed LAN/WAN services in you network.

Yes, the vlan has a specific subnet associated with it. The reason I asked is because we extend our phone system over a metro area network using a device called a Nortel Remote Office which converts analog phone wires to IP and then back again at the other end. So, it is not really VOIP, more like data, but I still need to make sure it gets priority. Thanks!

Mark Williams wrote:

Hello

I posted the question because we use a device (Nortel Remote Office) to extend our analog phones over a metro area network by converting the analog lines into IP and then back again. Everything works fine right now but we are replacing our ATM network with a Gig-E network and I want to make sure that our phones are not negatively impacted by this change because this.

Thanks

Hi, if you have GiG between the Nortel RO's, and each a single device in a VLAN - you will be fine. The layer 2 marking/CoS queuing is where phones and PC share a 10/100 port. To be sure, use layer 2 CoS marking on the port the RO is connected. By default, the switch will WRR (depending on switch) as the voice frames will have Layer 2 Priority. You should be looking at LLQ (Strict priority )and CBWFQ for Layer 3 QoS.

Plenty stuff on cisco if you keen -