Troubleshooting a scenario where Source remap is causing the VOIP issues

Troubleshooting a scenario where Source remap is causing the VOIP issues

SCENARIO / SYMPTOM

•    A PBX system contains 8 lines/extensions on the same device

•    Each line is assigned with separate extension numbers

•    Each line communicates with the PBX server with a particular source port (5060, 5160, 5163 etc..)

•    When the phone system initiates a SIP message for registration with the PBX server, each line/Extension communicates with their specific port configured on this phone system

•    When the traffic reaches the SNWL, it remaps each source port to another random port and sends it to the PBX server

•    The PBX server is already pre-configured to assign an extension to each source port which the phone communicates with

•    When the PBX server identifies a different random port number, it does not assign that extension to the phone, and those lines don’t work

Resolution for SonicOS 7.X

This release includes significant user interface changes and many new features that are different from the SonicOS 6.5 and earlier firmware. The below resolution is for customers using SonicOS 7.X firmware.

1. Navigate to POLICY | Rules and Policies | NAT Policies 
2. Create a NAT policy from LAN/VOIP zone or Phone system IP address to WAN by translating the LAN/VOIP subnet to WAN IP with the destination as any and services as any
3. Under the Advanced tab uncheck the option “Source port remap”
4. This option should allow the SonicWall to forward the source ports without any modification

Resolution for SonicOS 6.5

This release includes significant user interface changes and many new features that are different from the SonicOS 6.2 and earlier firmware. The below resolution is for customers using SonicOS 6.5 firmware.

1. Navigate to Manage | Rules | NAT Policies
2. Create a NAT policy from LAN/VOIP zone or Phone system IP address to WAN by translating the LAN/VOIP subnet to WAN IP with the destination as any and services as any
3. Under the Advanced tab, enable the option “Disable Source port remap”
4. This option should allow the SonicWall to forward the source ports without any modification