hi,
To configure port mapping on the ONT, perform the following steps:
IPv4 Port Mapping
Port mapping indicates that the Intranet server is allowed to be open to the Extranet (for example, the Intranet provides the Extranet with a WWW server or FTP server). Port mapping is to map the Intranet host IP address and port ID to Extranet IP address and corresponding port ID so that users from Extranets can access the Intranet server. With port mapping, the users cannot see the Intranet IP address and they see the Extranet IP address.
Navigation Path
Click Advanced > Forward Rules tab, and choose IPv4 Port Mapping. In the dialog box that is displayed, set the parameters related to port mapping, as shown in Figure 6-44.
Figure 6-44 IPv4 Port Mapping
Click Apply.
Configuration Example
Enable the packets sent from the WAN side to the ONT whose the destination WAN port number is 2000 to be forwarded to the LAN-side PC whose IP address is 192.168.100.20, and the port number is changed to 3000.

IPv4 Port Mapping
Port mapping indicates that the Intranet server is allowed to be open to the Extranet (for example, the Intranet provides the Extranet with a WWW server or FTP server). Port mapping is to map the Intranet host IP address and port ID to Extranet IP address and corresponding port ID so that users from Extranets can access the Intranet server. With port mapping, the users cannot see the Intranet IP address and they see the Extranet IP address.
Navigation Path
Click Advanced > Forward Rules tab, and choose IPv4 Port Mapping. In the dialog box that is displayed, set the parameters related to port mapping, as shown in Figure 6-44.
Figure 6-44 IPv4 Port Mapping
Click Apply.
Configuration Example
Enable the packets sent from the WAN side to the ONT whose the destination WAN port number is 2000 to be forwarded to the LAN-side PC whose IP address is 192.168.100.20, and the port number is changed to 3000.

thank you