Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

Strange Voice VLAN/trunking problem Catalyst 3560

I've run into a strange problem.

3560 switch, connected to a 7940 phone, port config as shown below.

I can connect some PC's (Windows 2000 and XP) to the phone and the config works as advertised (phone gets the voice vlan and the PC gets the data vlan.)

However, other PC's (just your average Dell or HP PC's) will not work at all unless the voice vlan is totally removed from the config, leaving both the phone and the PC on a single vlan. It obviously is some kind of weird mismatch between the PC and the switch port, but I am at a loss to make it work.

I've tried it all, static IP addresses on the PC for both the voice and data vlan. What have I missed?

Any suggestions?

3560 24 Port POE switch

Port config as follows

interface FastEthernet0/1

switchport access vlan 100

switchport mode access

switchport voice vlan 200

srr-queue bandwidth share 10 10 60 20

srr-queue bandwidth shape 10 0 0 0

mls qos trust device cisco-phone

mls qos trust cos

auto qos voip cisco-phone

spanning-tree portfast

spanning-tree bpduguard enable


Re: Strange Voice VLAN/trunking problem Catalyst 3560


I remember a similar problem, removing the 'spanning-tree bpduguard enable' command might help, can you try this ?



New Member

Re: Strange Voice VLAN/trunking problem Catalyst 3560

I'll check it out. This current problem exists in a remote office but I plan on duplicating it in a lab environment this week at the HQ.

New Member

Re: Strange Voice VLAN/trunking problem Catalyst 3560

did you find the solution?, i have the same problem, but the ip phone is a 7912g-a, just if both are in the same vlan, but if i use a 7912 g or 7960 it works.

switchport access vlan 2

switchport mode dynamic desirable

switchport voice vlan 1

switchport priority extend cos 3

mls qos trust cos

spanning-tree portfast

New Member

Have you tried something like

Have you tried something like this?  :


interface FastEthernet0/1
switchport mode trunk
switchport trunk native vlan 100
switchport voice vlan 200
switchport trunk allowed vlan 100,200