What commands do I use to configure QOS for FOIP

[rweir0001]

Hi,

Not sure where to post this question. I want to configure QOS for FOIP and need to know what commands to use? We have a Cisco switch connected to a fax server on one side, and our VOIP switches on the other. The fax line coming through the VOIP switches are using T.38 as it's protocol. I'm not entirely sure if it is T.38 Relay or PassThrough, but because they are also using the G.711 codec I believe that it is T.38 Pass Through.

I want to enable QOS on the interfaces that connect to the VOIP switches. The VOIP switches are third party and I don't have access to them. What commands should I use to enable QOS for FOIP?

[Joseph W. Doherty]

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Posting

QoS features can be very platform and/or IOS dependent, so when looking for suggestions for actual command usage, you need to specify the details for your equipment.

As to how your QoS might be configured, that depends on what you desire as a QoS policy, and what's your expected traffic usage.  I.e. you'll need to be a bit more specific that you just want to configure QoS.

[rweir0001]

We are trying to configure QOS on a Cisco WS-C3850-48T switch running IOS-XE. Essentially, we just want the FOIP traffic to be prioritized on certain interfaces. I no very little about QOS, so what other information would be pertinent? 

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

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In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Ah, well unfortunately, I haven't worked with the later 3K switches, like the 3850, so I'm unable to help you much there.  (BTW, some of the later switches now do ingress more like Cisco routers, i.e. by default, they trust everything.  Don't know if this applies to 3850 your switch.  Also BTW, again, it's important to list the actual IOS version being used, feature set/license being used too.)

As for other information, that would be your QoS goals.  You mention you want to prioritize FoIP on certain interfaces, but prioritize as in absolute, or just boost egress priority?  What about all your other traffic, etc.?

If you know very little about QoS, it might be best if you first learn a bit more about it and/or retain a QoS consultant.  The reason being, it's easy to have unintended consequences with QoS.

[rweir0001]

Thanks, Joseph. Yeah...I'm trying to fill my head with as much QOS knowledge as possible, but it is much more complex then I initially thought. I have learned that wired connections are implicitly trusted on my switch model. I also determined that I want to configure L2 QOS on our interfaces because we are not routing the traffic out. Our Cisco switch is connected to VOIP switches from another vendor that I don't have access to, so they are routing the traffic out, but I have no control over their configurations. So, with that said, L2 QOS is where it's at for me. I'm not having the best of luck narrowing my search down to JUST L2 QOS for my switch model, but I have found some information. I do have a consultant coming in tomorrow but I am trying to push this project as far as I can go, ideally to completion, before I even see him. With that said, my concern is that without enough QOS knowledge I'll create a bigger issue. 

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

It might help to understand, even if you're only doing L2 switching on your 3850, QoS features are pretty much the same.  On these kinds of L3 switches, you can use either L2 CoS or L3 ToS for classification.  I.e. you can still work L3 ToS QoS, while just doing L2 switching.