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Please refer to Upgrading to FreePBX 17 to know more about upgrade process.
A note for Chan SIP Support in FreePBX 17
Please note that, Freepbx 17 by default comes with Asterisk 21.
Asterisk 21 do not support chan_sip at all so please refer to below section if you like to use chan_sip with the Freepbx 17.
Using FreePBX 17 with chan_sip
How to upgrade to Freepbx 17 GA from FreePBX 17 Beta
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