Port configuration question

Unanswered Question
Dec 12th, 2008

We utilize VLANS and here is the port config from one of our switches:

switchport access vlan 31

switchport trunk encapsulation dot1q

switchport trunk native vlan 4

switchport mode trunk

switchport voice vlan 70

spanning-tree portfast

Am I correct in stating that the following is not needed:

switchport trunk encapsulation dot1q

switchport trunk native vlan 4

switchport mode trunk

Why would the previous three lines even exist in the port configuration?

I have this problem too.
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francisco_1 Fri, 12/12/2008 - 09:25

looks like the port is connected to a phone with a PC Daisy-chaining to the phone. the port is trunk because yuo have a data and voice vlan associating with the port. if that is the case then you need the trunking on the port.

If the port is connected to a single PC, then no need for the trunking. If the port is connected to another switch and carrying more than one vlan then you need the trunking.

Francisco.

kellyrudnick Fri, 12/12/2008 - 12:42

That makes sense. I do have phone on the the port and the PC connected off that. The data VLAN is 4 and the voice is 70. So I can see where it needs to be trunked so both VLAN tagged traffic can come down the pipe.

Thanks.

John Blakley Fri, 12/12/2008 - 09:25

It depends. If you have a device that has a default native vlan of 4 and you change it on this port back to 1, then you'll get vlan mismatch errors. The actual line that you don't need is switchport access vlan 31. You have the port in trunked mode right now, and the only way the other one will take effect is if you have "switchport mode access."

HTH,

John

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