Asus RT-AC1200G User Manual page 55

NOTE: When port forwarding is enabled, the ASUS router blocks
unsolicited inbound traffic from the Internet and only allows replies
from outbound requests from the LAN. The network client does not
have access to the Internet directly, and vice versa.
To set up Port Forwarding:
1. From the navigation panel, go to Advanced Settings > WAN >
Virtual Server / Port Forwarding tab.
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