Trouble shooting 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 those extension to the phone, and those lines don’t work

RESOLUTION/WORKAROUND

•    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 destination as any and services as any

•    Go to advanced tab and enable the option “Disable Source port remap”

•    This option should allow the SNWL to forward the source ports without any modification