Sip Ip Pbx

We just need to have an incoming call from outside to the IP PBX. Here, we use IP PBX Elastix and trixbox are. Thank you

Easiest way is to simply get a static IP address for the PBX, to a static NAT on the Cisco router and allow the ports. You must open port 5060 for SIP messaging and you must allow UDP ports 1024-65535 for RTP can be from one of these ports, it is dynamic. You'll have to adjust your access lists to such security. Most SIP providers I have dealt with the PBX want on a public IP address. Otherwise, you need to configure your router for voice and you have to do online peer to send calls to PBX, which is quite complicated and unnecessary in this case. I would recommend a static IP address. Last thing is to ensure that your PBX has reviewed the NAT settings if it has the option (most do).