Cisco3945 router QOS

[Mohammed Asif C Y]

Hi, We want to enable qos on Cisco router and the requirement what i have is, We have to give first priority to data always, Second priority to audio and Third priority to video Or Simple way Total bandwidth should be allocated Data 60% Audio 20% and Video 20%. Whenever the data is usage is not there, it should allow the audio and video for full usage. Is it possible to achieve in this router? if yes, can you please share sample configuration. Regards MAC

[Joseph W. Doherty · Accepted solution]

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Posting

Possible?  Should be.

class-map audio match-any

match . . .

class-map video match-any

match . . .

policy-map sample

class audio

bandwidth percent 20

class video

bandwidth percent 20

class class-default

bandwidth percent 40

Interface <egress>

service-policy output sample

[Rajib Das]

Hi Joseph, Thanks for the sample, what do you mean by match... , is it match any any ? Also Why do we need to create a class for default ?
How audio or video will consume entire BW while data traffic will not be present through this configuration , could you please kindly explain ?

Thanks & Regards,

RD

[Joseph W. Doherty]

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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

Match is the statement used within a class-map to "match" traffic you're want to include in that class.  Classes can be defined with match-any, which means any match statement will match the traffic for the class, or match-all, which means all match statements much be true to match the traffic for the class.

There's always a class-default, but when you define it, you can adjust its default values.  It's useful for "none of the above" (it's always listed last).

In your case, you'll likely need to explicitly match your video and audio traffic, but I assume your "data" would be everything else.  If so, a case where class default can be used.

The bandwidth statements sets minimum guarantees of bandwidth but does not preclude that class from using otherwise unused bandwidth, including all the bandwidth (again if not being used by other classes).

[Rajib Das]

Hi Joseph,

Thanks for your reply.

Is it possible to configure the QoS as first priority to data , Second priority to audio & Third priority to video ? If yes , then could you please help with a sample configuration of same.

Thanks & Regards,

RD

[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

For absolute priorities, for up to 4 classes, PQ would support that, but I don't think it's still supported on 3900s.

You can do it with two classes, using CBWFQ's LLQ, but you have 3 classes.

So, I'm unsure it's possible on a 3945.  Which might be just as well, because if it was supported, you might find, especially giving data first priority, you wouldn't like the impact to audio and video (assuming you would like the latter two to function).

Normally, for audio and video to work well, you need to guarantee them network performance, often better than guaranteed to data.  However, there are ways to also configure voice and video to not obtain more bandwidth then is allocated to them, this to avoid their "abusing" their special treatment.

[Rajib Das]

Hi Joseph,

Our traffic is consuming 100% BW currently. How can we check the configuration is working properly or not ?

Thanks & Regards,

RD

[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

It depends on what you're trying to confirm.

Sometimes using extended ping, with different ToS settings, will show class processing differences with production or artificial traffic.

Sometimes you need to generate artificial traffic, beyond 100%, and see if the far side receives what it should based on your policy.  Either artificial traffic with production traffic or without any production traffic.

NB: adding high volume artificial traffic to live production traffic will often degrade the production traffic.