linux – How to check ip-port mapping after adding a port-forwarding rule by firewall-cmd

In CentOS7, I have made a tcp relay by command “firewall-cmd –add-forward-ports …”.
However, now I need to know the mapping rules between incoming ip and the port assigned to the ip by NAT as the new source port.

Is there a translation table somewhere in my system or how can I get the in-time-mapping?
Now the only possible way I have thought out is to add some LOG rule in iptables where a forwarding is accepted.