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QoS a single port from 2960 across PTP link on 3750

I have spent a few hours researching different QoS settings and I want to hit my head on sharp objects. So I figured I would post here to get the advice of all you smart people

I have a server that generates a lot of traffic at times. I want to QoS this traffic and limit what it can use over a point to point fiber link that is only 50mbps.

The server is connected to a 2960-S with LAN Lite. The gateway of this network is a 3750 and this is where the connection for the point to point happens.

It's my understanding that I would need to tag the traffic on the 2960 and then policet on the 3750. But this is a little out of my wheelhouse for QoS (I normally just use it for VOIP so any help is much appreciated!)        

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Re: QoS a single port from 2960 across PTP link on 3750


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What you want to do, is "shape" the 3750's egress port (using the interface command srr-queue bandwidth limit) to not exceed your 50 Mbps, this to queue traffic on the 3750.

Then you want to direct your high volume bandwidth traffic to a queue dedicated for high volume that has been allocated a low bandwidth guarantee percentage (insuring more important traffic isn't delayed by it, yet still allowing the high volume traffic to take advantage of all available bandwidth).

Unfortunately, you direct traffic to queues based on either L2 CoS or L3 ToS markings (I recommend to use the latter).

If the 2960-S can identify your server traffic and if it can mark it (which might be as mark all traffic on one port with such-and-such marking), you would then look for that on your 3750.  (I not very familiar with the 2960-S with LAN Lite, so don't know if this can be done.)

If the 2960-S cannot identify/mark your server traffic, the 3750 can have an ingress policy to analyze (i.e. IP addresses?) and mark traffic.

There's much more involved in doing QoS correctly on 3750s, especially regarding buffer management.  Too much, unfortunately, for me to just post a few statements and write "do this".

Done correctly, you may see a huge improvement with QoS.  If you want to pursue this, I can reference documents on Cisco's sites that will provide the information you know, but they will likely require much study.  Or, hire some consulting time of a QoS expert.

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