RingCentral Phone System. Whats teh best way to setup in a 100F?

Hi BRegi,
 

The SIP provider will advised to disable the SIP ALG and SIP session helper both or to disable only SIP ALG. 

https://docs.fortinet.com/document/fortigate/7.6.6/administration-guide/147933/sip-alg-and-sip-session-helper#:
 

To optimize your FortiGate 100F for a RingCentral phone system, you may check with SIP provider team and disable SIP ALG. By default, FortiGate's built-in SIP inspection intercepts and modifies VoIP packets, which may causes RingCentral issues like dropped calls, registration failures, and one-way audio
 

Reference Link: https://community.fortinet.com/fortigate-3/technical-tip-disabling-voip-inspection-96221
 

Configure dedicated firewall policy for RingCentral traffic, allow required SIP/RTP ports, and use the RingCentral ISDB object as a destination with ALL Security Profiles disabled and using Flow-Mode inspection. This will ensure that all communication (port/protocols) to/from RingCentral's networks passes unfettered.
 

Please refer to the article below which provides a list of resources that can be used to configure and troubleshoot VoIP on FortiGate:
 

https://community.fortinet.com/fortigate-3/technical-tip-voip-and-sip-configuration-and-troubleshooting-resource-lists-182665
 

If you have found a solution, please like and accept it to make it easily accessible to others.
 

Regards,
Aman