Issue with NAT Loopback on Flint 2 (GL-MT6000) – Unable to Access Internal Server via Public IP from LAN

Routers
2

Hi,

I tested on my MT6000 with v4.8.2-op24 and did not reproduce the issue.

My topology is as follows, and the Internet is not a real public network, which is simulated by a router:

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The MT6000 is configured as follows

  1. Set up port forwarding:

    Bruce_2025-09-09_15-35-54
    Bruce_2025-09-09_15-35-541290×922 56.4 KB

  2. Full Cone NAT enabled. If not enabled, LAN/WiFi and WAN access is also normal.

    Bruce_2025-09-09_15-36-50
    Bruce_2025-09-09_15-36-501303×389 20.1 KB

The PC_ B from the Internet (WAN side of MT6000), it is without issue to access through [WAN IP:port]:

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Bruce_2025-09-09_15-39-59614×746 33.5 KB

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Bruce_2025-09-09_15-40-31547×601 13.3 KB

Bruce_2025-09-09_15-40-50
Bruce_2025-09-09_15-40-50590×593 40.7 KB

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Bruce_2025-09-09_15-42-201276×780 112 KB

The PC_ A connected to MT6000 WiFi, access through [WAN IP:port], without issue (one example here)

Bruce_2025-09-09_15-44-20
Bruce_2025-09-09_15-44-20909×801 129 KB

Please reset firmware and try to re-configure.
Every time you did a configuration, and check [WAN IP:port] to see which configuration occurs exception.