Hi all, 

I’m experiencing a persistent issue with my TP-Link AX50 router (Firmware version: 1.1.1 Build 20250917 rel.63889(4555)) where upload speeds are severely throttled when IPv6 is enabled.

Issue Summary:
With IPv6 enabled, upload speeds drop to near-zero regardless of device, cable, or LAN port.
Speedtest.net reports a socket error during the upload phase:
“A socket error occurred during the upload test. A firewall could be blocking the connection or the server might be having some issues.”

Disabling IPv6 immediately restores full upload performance (~500 Mbps), confirming the issue is IPv6-related.
Troubleshooting Steps Taken:

• Verified 1 Gbps full duplex link on both WAN and LAN ports.
• Swapped cables and tested multiple devices.
• Disabled QoS, NAT is enabled, traffic monitor and antivirus are off.
• No firmware updates available.
• Router CPU and memory utilization are normal (35–45% CPU, 45% memory).
• MTU verified at 1500 with no fragmentation.
• Wireshark confirms outbound QUIC/TCP traffic stalls during IPv6 upload attempts.

This appears to be a firmware-level issue with IPv6 handling or NAT offload.

Can you confirm if this is a known issue, and whether a fix is planned? I’m happy to provide further diagnostics or packet captures if needed. Should I roll back to an earlier firmware version?