Consistent NAT

1. Click on VoIP
2. Click on Settings
3. Set Enable consistent NAT to enabled
4. Every other checkbox on this page should be unchecked as well.
   
5. Click Accept

Advanced Firewall Settings

1. Click on Firewall Settings
2. Click on Advanced
3. Set Enable Stealth Mode and Randomize IP ID to disabled.
   
4. Click Accept

Create Custom VoIP Services

1. Under Network > Services click Add...
2. Fill the popup as follows:
   • Name: VoIP RTP
   • Protocol: UDP
   • Port Range: 3000 - 65000
   • Sub Type: None
3. Click Add
   
4. Click on Service Groups > Add Group...
5. Name: VOIP Services
6. Add the following services to the right box
   1. SIP
   2. VoIP RTP
7. Click Add
   

Create LAN > WAN Rule for Services

1. Navigate to Firewall > Access Rules
2. Click on Matrix
3. Click on the arrow under LAN > WAN
4. Click on Add...
   • Source Port: Any
   • Service: VOIP Services
   • Source: Any
   • Destination: Any 
   • Users Included: All
   • Users Excluded: None
   • Schedule: Always On
   • Comment: QoS for VoIP Phones
   • Enable Logging: True
   • Allow Fragmented Packets: True
     
5.  Click on the Advanced tab
   • UDP Connection Inactivity Timeout (seconds): 90
     

Create Address Group for Voice Services

1. Click Firewall > Address Objects > Add
2. Fill out the following: 
   • Name: Name of the Assignment 
   • Zone Assignment: WAN
   • Type: Host
   • IP Address: IP of the Server
     NOTE: Find IP Addresses and Ports here
3. Add each IP Address for Voice Services as an Address Object
   
4. Create an Address Groupand add the address objects that were created
   • Name: Voice Services

Excluding Voice Services IPs under Security Services (if applicable)

1. Click Security Services 
2. Check each Service and see if it is enabled
3. If so, you need to enable the Exclusion List on each service and set it to Voice Services
4. Example: Content Filter
   
5. Once you exclude it, click Accept