Environment

• Router: TP-Link ER707-M2 F/W: 1.4.2 Build 20260509
• Controller: TP-Link Omada OC200 F/W: 1.40.18 Build 20260506 Rel.74003
• WAN Type: PPPoE + SLAAC + Prefix Delegation (IPv6 Dual Stack)

Network Configuration

• IPv4 DNS: Quad9 (DoH enabled initially, later tested with ISP DNS)
• IPv6 DNS: Quad9 IPv6 (also tested with ISP IPv6 DNS in plain mode)
• IPv6 Status: Enabled and fully functional
• Client IPv6 test: 10/10 (confirmed working)
• IPv6 Prefix: Delegated correctly (/64 observed)

Issue Description

When IPv6 is enabled on the WAN interface, the built-in Omada Speed Test function fails consistently on the ER707-M2 when managed via OC200.

The issue is reproducible and occurs under all tested DNS configurations.

Expected Behavior

• Speed Test should run normally regardless of IPv4/IPv6 configuration
• If IPv6 path fails, system should fallback to IPv4 automatically
• WAN connectivity should not affect internal speed test execution

Actual Behavior

• Speed Test works normally when IPv6 is disabled
• Speed Test fails immediately when IPv6 is enabled on WAN
• Error shown: “Fail” (no additional diagnostic details provided)
• No relevant event/log entries are generated in OC200 or gateway logs

Reproduction Steps

1. Configure ER707-M2 with PPPoE WAN (IPv4 only)
2. Run Speed Test → Success
3. Enable IPv6 (SLAAC + PD)
4. Confirm IPv6 is working (client test: 10/10)
5. Run Speed Test → Fail
6. Disable IPv6
7. Run Speed Test again → Success restored

Additional Testing

• Changed DNS configuration:
  • Quad9 DoH (IPv4)
  • Quad9 IPv6 (plain DNS)
  • ISP DNS (IPv6 + IPv4)
• Result: No change, Speed Test still fails when IPv6 is enabled
• Internet connectivity remains fully functional in all cases
• IPv6 routing confirmed stable via external tests

Impact

• Built-in Speed Test becomes unusable when IPv6 is enabled
• Monitoring/diagnostic reliability of Omada controller is affected
• May lead to false assumption of WAN failure despite normal connectivity

Workaround

• Disabling IPv6 immediately restores Speed Test functionality
• However, this is not a viable long-term solution for dual-stack environments

Conclusion

This appears to be a compatibility issue or bug in the Omada Speed Test implementation when IPv6 is enabled on WAN interfaces.
IPv6 connectivity itself is fully functional and verified; the issue is isolated to the Speed Test feature.

This context generate by AI after few hour talking and summary of result. Any body have ever face to a problem same like this please share