My Windows 11 laptop recently stopped detecting the router's NAT type. NAT checkers cannot identify the laptop's IPv4 information in the NAT-related results, even though other IP-checking sites display it normally. Other devices on the same router show a moderate NAT, but this laptop reports that NAT is unavailable. As a result, Steam, voice chat, online games, and other apps that need peer-to-peer communication no longer work, while browsing and video streaming are fine.
The problem happens only on this particular Wi‑Fi network; the laptop works differently on other networks. I have already reset the router and PC firewall settings. I also noticed that Teredo appears to be disabled. I can set it to enterpriseclient, but Windows will not let me restore the default setting. Could this be caused by the router, Windows, Teredo, or a combination of issues?
2 Answers
The Teredo setting is probably a symptom rather than the root cause. Teredo can help IPv4-only devices communicate with IPv6 services while behind NAT, but changing it to a particular client mode will not repair a router or an application that is being blocked. Check the affected apps’ firewall permissions and test whether IPv6 is enabled on the adapter and router. Also make sure the laptop has a normal private IPv4 address and default gateway, rather than an address from an isolated guest network.
Because normal web traffic works but several communication-heavy apps fail, a local VPN, security suite, proxy, or damaged Windows networking configuration could also be involved. Temporarily disable or uninstall any VPN and third-party network filter, then try resetting the Windows network stack with an elevated Command Prompt using commands such as `netsh winsock reset`, `netsh int ip reset`, and `ipconfig /flushdns`, followed by a restart. Windows Network Reset can also reinstall the adapter.
If the laptop works normally on a phone hotspot but not on this router, compare the router’s settings and test with UPnP enabled. If it fails on every network, focus on Windows or security software instead of Teredo.
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