Voicemail Pro not responding with IPO

 What

The Voicemail Pro service running on an Windows domain controller can give problems on network communication

 Problem

De VM Pro service runs on ports, that can be used for the DNS service also.

 Solution

After running VM Pro on their Windows domain controller fine for a few months, VM Pro decided to stop communicating with the IPO.  It looked like everything was fine, but obviously there was no communication between the IPO and VMPRO.  This is because MS DNS decided to eat the ports needed by the VM PRO to communicate with the IPO (UDP 50791-50801)...

If you experience Voicemail Pro Not Operational, but it seems fine... and you get this:

In Monitor:

3233269mS CMTARGET: 5.20.1 27 Q931 Trunk:5 CHAN=1: TimerExpired cause=CMTCNoAnswerTimeout
3233269mS CMTARGET: 5.20.1 27 Q931 Trunk:5 CHAN=1: Retarget NOANSWER EXCEPTED=00000001 ValidTargets=1
3233269mS CMTARGET: 5.20.1 27 Q931 Trunk:5 CHAN=1: Retarget on target_cfg_user=SMConference
3233269mS CMTARGET: 5.20.1 27 Q931 Trunk:5 CHAN=1: ADD USER: SMConference depth=1 disallow_cw=0 dnd=0 real_call=1
group_call=0 type(CMNTypeUnknown) incl(0x1) excpt(0x1), allow_redir(1) remote=00000000
3233270mS CMTARGET: 5.20.1 27 Q931 Trunk:5 CHAN=1: SELECT: TRY VOICEMAIL orig_hg() orig_user(8509)
3233270mS CMTARGET: 5.20.1 27 Q931 Trunk:5 CHAN=1: ADD VM TARGET
3233270mS CMTARGET: Voicemail Pro not operational
3233270mS CMTARGET: 5.20.1 27 Q931 Trunk:5 CHAN=1: ADD VM TARGET: FAILED availability=0
3233271mS CMTARGET: 5.20.1 27 Q931 Trunk:5 CHAN=1: VM targeting failed. Remaining on final target SMConference
3233271mS CMTARGET: 5.20.1 27 Q931 Trunk:5 CHAN=1: GetNoAnswerTimer:22

Microsoft DNS will fight for ephemeral IP ports with DNS.  One way to test this is to shutdown the MS DNS server, restart VM Pro and then restart MS DNS. 
If THEN your server is working you need to reserve the IP office ports so Microsoft DNS can't grab them:

Start Registry Editor (Regedit.exe).
Locate and then click the following registry subkey:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

On the Edit menu, point to New, and then click Multi-string Value. There may be an entry already there, just modify it.

Right-click the new value, click Rename, type ReservedPorts, and then press ENTER.

Double-click the ReservedPorts value, type the range of ports that you want to reserve, and then click OK.

Add 50790-50801

Click OK.

Quit Registry Editor.

Restart your voicemail pro system (full reboot)... now your MS DNS will not try to grab ports that VM PRO needs to operate.