cisco ASA 5525 with Voip

 i have Cisco ASA5525 and ucm 3cx voice server i want to use external extension for makes call from anywhere  
i have one public  ip in firewall ASA5525
and one ucm 3cx ip address local
i need to make NAT for sip port 5060 from public ip to local ip
and RTP ports 10000 to 20000 to local

anyone can help me what is the right command i have to do in cisco ASA
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Mustafa Al HousamiNetwork and Security Consultant/CCIE #48377Commented:
First, your setup is not recommended for security reasons (to not expose your PBX for toll fraud attacks).
Second, NATting RTP ports may not work fine over internet.
What I suggest is to configure remote access VPN on Cisco ASA and let the extension to register over VPN then make external calls.

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Mustafa Al HousamiNetwork and Security Consultant/CCIE #48377Commented:
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