• SonicOS and SonicOSX 7 VoIP
• VoIP
  • VoIP Security
    • Security Appliance Requirements for VoIP
  • VoIP Protocols
    • H.323
    • SIP
  • SonicWall’s VoIP Capabilities
    • VoIP Security
    • VoIP Network
    • VoIP Network Interoperability
    • Supported Interfaces
    • Supported VoIP Protocols
      • H.323
      • SIP
      • SonicWall VoIP Vendor Interoperability
      • CODECs
      • VoIP Protocols on which SonicOS/X Does Not Perform Deep Packet Inspection
    • BWM and QoS
      • Quality of Service
    • How SonicOS/X Handles VoIP Calls
      • Incoming Calls
      • Local Calls
• Settings
  • Configuring VoIP Settings
    • General Settings
    • SIP Settings
      • Enabling SIP
    • H.323 Settings
      • Configuring Bandwidth on the WAN Interface
      • Configuring VoIP Access Rules
  • Configuring VoIP Logging
• Call Status
• SonicWall Support
  • About This Document

General Settings

There is one option under General Settings: Enable Consistent NAT.

Consistent NAT enhances standard NAT policy to provide greater compatibility with peer-to-peer applications that require a consistent IP address to connect to, such as VoIP. Consistent NAT uses an MD5 hashing method to consistently assign the same mapped public IP address and UDP Port pair to each internal private IP address and port pair.

For example, NAT could translate the private (LAN) IP address and port pairs, 192.116.168.10/50650 and 192.116.168.20/50655 into public (WAN) IP/port pairs, as shown in IP address and port pairs.

IP Address and Port Pairs

Private IP/Port	Translated Public IP/Port
192.116.168.10/50650	64.41.140.167/40004
192.116.168.20/50655	64.41.140.167/40745

With Consistent NAT enabled, all subsequent requests from either host 192.116.168.10 or 192.116.168.20 using the same ports illustrated in IP address and port pairs result in using the same translated address and port pairs. Without Consistent NAT, the port and possibly the IP address change with every request.

Enabling Consistent NAT causes a slight decrease in overall security, because of the increased predictability of the address and port pairs. Most UDP-based applications are compatible with traditional NAT. Therefore, do not enable Consistent NAT unless your network uses applications that require it.

For Consistent NAT to work properly, the minimum time interval between calls must be at least 200 msec.

Enabling Consistent NAT

To enable consistent NAT

1. Select the Enable Consistent NAT option. This option is not selected by default.
2. Click Accept.