Support for Cisco's "Voice VLAN"

I'm not a Cisco expert but is it possible to use the dynamic mode like this?

switchport mode dynamic desirable
or
switchport mode dynamic auto

If the phone can send DTP signal, I think the port would become a trunk automaticaly.

Let me know the results.

Not that surprising, since they're a subsidiary of Cisco.

I just found out that DTP is a Cisco proprietary protocole also.

Too bad

I've tried every way I can think of to make this work, and it just doesn't.

If you want to run the PC and phone on different VLANs, then you have to force the Cisco switch port to trunk. Then when you pull the phone out of the chain, you have to set the port to access or dynamic.

Using native vlan doesn't work, because the switch will forward all traffic for that VLAN _untagged_. If the phone is in trunk mode ("VLAN enabled") then it ignores the packet because there's no tag, it never goes out of the phone to the PC.

I've tried setting the switchport to "mode dynamic auto" and "mode dynamic desirable." The phone won't go into trunk with either setting. As far as I can tell it is purely trunk or purely access, based on the setting you choose.

This is a significant issue in our endpoint selection. We don't necessarily care whether it supports CDP, DTP, or any other Cisco protocol specifically. We just want to be able to pull the phone out the daisy chain and run directly from switch to PC w/o re-configuring the switch port, however that might be accomplished.

Would anyone from Aastra care to weigh in on this? We really like the phones other than this issue, but it's a significant one.

Thanks!

What phone and switch are you working with? Would you be willing to post your switchport configuration? I don't see how you're getting the access vlan directly to the PC without changing the mode to access or dynamic?

I'm testing with an Aastra 57i and a Catalyst 3560G. My switchport config is like this:

interface GigabitEthernet0/9
switchport access vlan 89
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 89,189
switchport mode trunk
end

89 is my data vlan and 189 is my voice vlan. This works fine with the PC daisy-chained from the phone, but if you try to plug a PC directly into the port, you won't get anything. This is how it's supposed to work, because the port is set to trunk (definitely, unequivocally, un-dynamically trunk). Trying to set the mode to dynamic trunking doesn't work with this phone.

The only way I know to attach a PC directly to a trunk port is to set the native vlan. With the native vlan defined, I can attach a phone to the port, I can attach a PC to the port, but I can't daisy-chain a PC off the phone. The phone doesn't seem to know what to do with the un-tagged traffic, because it's set to trunk mode.

I can see how it would work with 3 vlans:

interface GigabitEthernet0/9
switchport access vlan 89
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 89,189
switchport trunk native vlan 11
switchport mode trunk
end

Now, when you have the PC daisy-chained, you would get 89 on the phone and 189 on the PC, and when you plug the PC directly you would get vlan 11. But this is just goofy.

Thanks for your help.