@Geotrupus interesting that yours seems to be working again, I also disabled those features and restarted but still see ongoing issues. Are you using PPPoE for your WAN connection?

  @Geotrupus I have DPI disabled on my side and no improvement unfortunately, I actually had this disabled before and after the update.

  @cykz Yes, it's a PPPoE connection (1 Gbit/s Fiber Link from Deutsche Telekom) 

  @cykz You may check if you have any other TLS Layer-related services enabled (Proxy / DPI / DNS Proxy / Secure DNS / DoH/DoT). I guess the bug is related to the TLS / OCSP layer - somehow.  

  @Geotrupus I dont have, ids, dpi nor doh enabled.. still having the issue.

Edit checked it again... all off rebooted an extra time.. still not working.

Hey, I have a quite similar issue regarding ER8411, and PPPoE WAN:

 

Most of the http/2 traffic, especially in apps like Cursor, Docker on Windows (in WSL) did fail until i set the MTU on the windows adapter to 1492.

I have a ER8411 gateway, latest firmware. No clue if MSS-Clamp borked or PMTUD failed, but setting the MTU to regard the PPPoE header seems to fix the situation.

Of course its not a solution for all devices in my network, but for now it works for me. I eventually have to switch to the Fritzbox in DMZ again, if TP Link won't fix this.

It can't be an IPv6 issue, i have full dual stack at my provider - and the issues persist disabling the stack on wan and LAN.

It's also possible that the gateway doesn't play well with multi WANs and different MTU there, since my other WAN is a 1500 MTU uplink to a router/modem (that does the clamping just fine). I tried setting the 1492 MTU on all enabled WAN ports, but that didn't help.

Of course, all kind of processing, IDP or QoS is disabled, but I have setup policy routing and do failover myself toggling the policies for my two WAN uplinks.

  @fr34kyn01535 Hey im the guy from reddit! thankyou for posting!

I can confirm on my windows machine this worked:

```

PS C:\Users\john> netsh interface ipv4 set subinterface "Ethernet" mtu=1492 store=persistent
Ok.

PS C:\Users\john> function Test-Connection-Pattern {
>>     param(
>>         [string]$Url,
>>         [int]$Attempts = 10,
>>         [int]$Timeout = 10
>>     )
>>
>>     1..$Attempts | ForEach-Object {
>>         $code = curl.exe -s -o nul -w "%{http_code}" --max-time $Timeout $Url 2>$null
>>
>>         if ($code -eq "000") {
>>             Write-Host "Attempt $_ - FAILED" -ForegroundColor Red
>>         } elseif ($code -match "^(200|302)$") {
>>             Write-Host "Attempt $_ - SUCCESS ($code)" -ForegroundColor Green
>>         } else {
>>             Write-Host "Attempt $_ - $code" -ForegroundColor Yellow
>>         }
>>
>>         Start-Sleep -Seconds 1
>>     }
>> }
PS C:\Users\john> Test-Connection-Pattern -Url "hxxps://[URL]" -Attempts 5 -Timeout 3
Attempt 1 - SUCCESS (302)
Attempt 2 - SUCCESS (302)
Attempt 3 - SUCCESS (302)
Attempt 4 - SUCCESS (302)
Attempt 5 - SUCCESS (302)
```

I think i solved it!!!

I set the custom dhcp option with a lower MTU value and it worked!

  @-CyRaX- Thanks for the update & suggestion! Did you reverse the windows machine "fix" before testing? I am trying this DHCP setting but so far still seeing failed requests, will keep testing.

  @cykz i did not reverse the netsh fix. After appling the dhcp option. I reconnected my phone to wifi. Then the apps started working again.