Ip telephone ringing but no voice being transported
Confirmed 7/20/2026
Problem
Ip telephone ringing but no voice being transported
Symptoms
both parties of a voip call cannot hear each other although the phone ringing.
Environment
FortiGate
FortiOS version
all Versions
Root Cause
In this case it is mostly that the VOIP proxy is enabled and trying to look into and scan the voip packets which is causing the packets become corrupt
Solution
running the following Commands should help disable the VOIP proxy:
config system settings set default-voip-alg-mode kernel-helper-based End
Delete the SIP protocol from the Session helper:
config system session-helper delete (SIP ID) end
Delete all Sessions with port 5060 (SIP Port), deleting the sessions help that all new created sessions will go through the voip with the new Configurations:
diagnose sys session filter dport 5060 diagnose sys session clear
Verification
voip calls should now works fine
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