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Walkthrough Wednesdays
Sergey Balyura

voice loss with the huge data sending through the phone

Hello, everybody!


need help!


I have CUCM 7.1

I have a lot of "phone+PC" sets where PS' cable inserted in a phone. and phone is going into the switch


I've discovered that when I put a big shunk of data from PC to anywhere the voice from me is degraded. the other side receive a lot of voice drops.


it repeats even if both the phones are on the same switch.


I looked into the "show interface". there is no drops in input queue of my interface.


maybe the built-in switch in the phone works not good...


please help :)


thank you very much for your help.


"priority-queue out"command was inserted by "auto qos voip cisco-phone".


about trusting - "mls qos trust dscp" equals to "trust to all frames", even to PC frames. I do want to trust only to cisco-phone frames.


I will try to run "auto qos voip cisco-phone" on the other port.


and will sniff, yeah.


hello again!


well still no success


"auto qos voip cisco-phone" on other side did not help


I sniffed the traffic from my port. I see phone send DSCP EF, PC - DSCP 0. that is ok

and I couldn't find CoS metrics in wireshark dump...


any thoughts, please?

Difficult issue. It may be the phone or even the model. Suggest trying the same test with different phones. Possibly once with the same type then again with a different model. Best tested with phones on the same switch with auto qos be applied to all interfaces involved. (You should be doing that anyway).


You could try different ports on the switch.


Finally, in the absence of getting any other indication as to what's going on and although the interfaces look clean it may be a good idea to try testing with the phone connected directly to the switch and not via in house cabling. There may be the off chance the house cabling performance degrades at higher data rates.


If all else is inconclusive and it can't be isolated to the phone type, infrastructure, configuration then a CCO case may be in order. If I think of anything else I'll let you know.




thanks a lot.
I tested it already on different models, on different switches.
and I cannot isolate it to anything except the input priority problems...

hi everybody!


shame on me. it was a storm control unicast.

it drops packets... not only traps...

delete it. and everything is ok now.


thanks a lot :)

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