03-24-2009 09:41 AM
Just to clarify I guess I asked wrong question because the Voice VLAN needs to be supported by the switch (and has nothing to do with the phone itself) and the phone will work as long as it supports vlan tagging.
03-24-2009 10:59 AM
This message was edited by merlin on 3-24-09 @ 11:00 AM
05-25-2009 08:54 PM
Here is what I discovered:
All phones will work if the telephone system is on the same subnet. Also all phones can be put on voice vlan because we can configure a switch port to tag packets for this particular port but the problem is that whatever is plugged to the back of the phone will be also on this vlan - unless we set up security and whatever is not from the phone will be dropped making the PC port on the back of the phone useless.
NOT all 3Com phones support (whatever support means) vlan tags. The auto mode of voice vlan will not work on remote subnet for 21xx rev A phones for example ,I have not tested rev. b and above of 21xx series, 31xx works!. The 21xx rev A will simply not accept the DHCP 184 suboption 3 (vlan ID) and will remain on the default vlan (untagged on the port that it is plugged in).
From what I observed in order for the phone to "support" vlan tags on remote subnets the phone needs to have the option to tag packets by itself (21xx rev A cannot do this) - if the phone does not have the ability to tag packets the phone simply sends untagged packets to the switch and the switch needs to tag them which whatever is setup for this port.