We have a WIN2K8 server that runs DHCP for the data VLAN and has a scope 192.168.1.0/24. This server is attached to an HP Procurve switch in the data VLAN – VLAN 1 as UNTAGGED. In this scenario, all works fine; 1) the PCs get a Data IP address and the Phones boot, receive a data IP address along with some options that tell the phone to tag packets in VLAN 2. 2)The phone releases the data DHCP address, reboots, requests a DHCP address again (but this time in VLAN 2 as the packet is tagged) , receives a VOICE DHCP address (192.168.2.0/24) from the IP PBX and all works well! IF, we add the WIN2K8 server switch port to be not only on the data VLAN (1) as untagged, but also add that port to the VOICE VLAN (2) as tagged (standard IPT switch config) then the scenario in part 1) above still works but part 2 fails! What seems to happen is that in part 2), the WIN2K8 server sees the tagged DHCP request for VLAN 2 and issues ANOTHER VLAN IP Address – 192.168.1.0/24. The phone then hangs as there is no PBX to download firmware from as it is in the DATA subnet (192.168.1.0/24) but on VLAN 2 at layer 2 which is 192.168.2.0/24. The strange thing is that this worked for 3 years with a WIN2K3 server and only happened after it was replaced by the WIN2K8 server! Any help greatly appreciated.

Hi nick, Thanks for posting here. I think this issue occurred because of redundant DHCP services in same layer 2 broadcast domain. You mentioned that this issue occurred after you set server connect to 2 VLANs in same time , so I understand that clients are going to be (mostly) randomly assigned addresses by DHCP server and PBX. The one that answers the client's DHCPDISCOVER request first is going to end up assigning the address to the client. I think this is not a good idea . And could you describe detail about what options you did on your DHCP server so that IP phone tag packets in VLAN 2? Thanks. Tiger LiPlease remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Hi nick, Seems you had unmarked my answer, If you have any further questions or concerns, please do not hesitate and let me know. Thanks. Tiger LiPlease remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.