cos value , ip phone ,PC setting cos?

[sarahr202]

Hi everybody.

Sw1---------------ipphone

                                    |

                                    |

                                 PC

By default ip phone does not trust cos values received in frame from attached PC.  My book says we can use the command:

switchport priority extend trust  on a switch to instruct ipphone to trust COS  values from PC.

But how could Pc set COS values considering that there is no trunk link between iphone data port and PC?

thanks and have a great weekend.

[Reza Sharifi]

Hi Sarah,

In this case COS, value applies to the voice vlan.

sorry, your wirting appeard long after the picture.

HTH

[Kishore Chennupati · Accepted solution]

Hi Sarah,

I believe when they say that its most likely based on the assumption that you can configure the port on the iphone to be a trunk. I tested it once by configuring the phone port to be trunk and connected a switch behind it for testing ;-) and it seemed to have worked. Lets say your PC is running VM's in that case its acts like a server with multiple vlans and you can trunk it to the iphone etc. I guess you can test it in your lab or something.

HTH

Regards, Kishore

[Reza Sharifi · Accepted solution]

Hi Sarah,

switchport priority extend trust

With the command above you enable the phone to trust the priority it receives form the PC.If you apply

switchport priority extend cos 4

than the phone will override the default value of 0 to 4

HTH