Asterisk behind the Cisco RV042 One-to-One NAT

I am trying to configure my Asterisk server behind the Cisco RV042. I’ve got several external IP, so I decided turn on One-to-One NAT in my Cisco RV04. I thought that this is better solution than port forwarding featured. But for now it doesn’t work correctly.

In my local net everything is ok with SIP calling. The problem is when I am trying to connect from the Internet.

Here is my sip_nat.conf. I am using Elastix.

localnet= ;
externip=94.75.xx.x ;

qualify=600 ;
media_address = 94.75.xx.x ;

There is no sound when I am calling to the test number 1234 from the Internet. Connection is initialized, but after 6 sec it disconnected…

How can I solve my problem? What solution is better? One-to-One NAT or port forwarding?
Does anyone work with Cisco RV042 and Asterisk?