dynamic tagged and untagged vlan assignment

[Phil Mayers]

Ivan Kalik wrote:
>> The phones need to be in a tagged vlan instead of an untagged.
> 
> Are you sure about that? You tag VLANs on a trunk port. And that port
> will be connected to the upstream device, not your phone.

No, it's quite common for VoIP hardphones to have a passthrough port - 
effectively a 3-port switch - one facing the network, one facing the 
desktop PC, and one facing the phones internals. It's quite common to be 
able to put the phone on the tagged vlan and the PC on the untagged. 
It's less often useful IMHO, but "Cisco say so" is often the reason ;o)

For interest: obviously the phone needs to know the tag number. LLDP-MED 
is the "normal" way of signalling this, or CDP on all-Cisco networks.

Responding to the OP, whether you can do this and the syntax to use 
depends on your switch. For example with 3Com 4400 and (I think) Extreme 
x450 you do this:

  Tunnel-Type = VLAN,
  Tunnel-Medium-Type = IEEE-802,
  Tunnel-Private-Group-id = "20 30t"

...to put vlan 20 untagged and 30 tagged.

Some switch vendors may require a VSA to put a tagged vlan. What model 
switch are you using?