How to configure a Cisco router so that internal IPs are not visible behind NAT?

Question

Computer networks

Good afternoon.
There is a Cisco RV320 router and there is cloud telephony.

The problem is the following:
Before the new year, the SIP telephony provider replaced the server through which telephony works and now the system blocks phones because, according to information from the provider, requests for their equipment do not come from external IP, but from all internal IPs (that is, gray IPs enter the network ).

The question is, how to properly configure so that all internal / gray IPs are visible only inside the network, and not from the outside?

According to the documentation, this is configured in the One-to-One NAT section:
https://www.cisco.com/c/en/us/support/docs/smb/rou...

But when configuring, I get the following error:


What is not doing so? White ip from the provider is one.

Answer 1

What is TA? some have a setting to work behind NAT. in general, it would be cool if you took a traffic dump on the external interface of the router. It would be possible to determine what and where is wrong. Well, since you have such questions, then try ALG.