poor inbound auido quality T5XW

[jwmilleril]

We have a bunch of T54W and T57W phones with the PC connected to the PC port on VLAN 1 and the Audio is on VLAN 50 all auto provisioned using the 3cx out of the box templates. Pretty regularly when on a call, the inbound audio will start to garble. The outbound audio is not impacted. We can reproduce this problem if we do a speed test on the PC while on a call indicating (to me anyway) that QoS isn't working correctly. If I insert a managed switch on the same LAN jack to separate the PC from the phone, the problem goes away. But, I obviously don't want to purchase POE switches for the whole company. Oddly enough, we don't seem to be able to reproduce the problem on a T46S.

Any ideas?

[jwmilleril]

We discovered the issue. We configure our cisco switch ports to define the voice vlan as 50. We also set the provisioning configuration for the phones to assign vlan50 to the wan interface of the yealink. This works fine in the T46s but not the T5X phones. By leaving those VLAN assignments blank on the 3cx settings, all is well.