Fix BBR2 bugs on Windows 11

Question

Hello I have changed the congestion provider to BBR2 with the command

netsh int tcp set supplemental Template=Internet CongestionProvider=bbr2
netsh int tcp set supplemental Template=Datacenter CongestionProvider=bbr2
netsh int tcp set supplemental Template=Compat CongestionProvider=bbr2
netsh int tcp set supplemental Template=DatacenterCustom CongestionProvider=bbr2
netsh int tcp set supplemental Template=InternetCustom CongestionProvider=bbr2

I am running on Microsoft Windows [Version 10.0.26100.3915]

There appears to be multiple bugs, it breaks Steam as the Steamwebhelper fails to launch anymore, and when using Internet Download Manager it breaks all download hooking when changing back to CUBIC they work again, from what I can gather It breaks 'localhost' (the loopback interface) TCP traffic leading to slow or unresponsive connections within the same machine.

Best Regards.

Answer 1

You have to execute these two commands in case connectivity is broken with BBR2:

netsh int ipv6 set gl loopbacklargemtu=disable
netsh int ipv4 set gl loopbacklargemtu=disable

Answer 2

netsh int ipv6 set gl loopbacklargemtu=enabled netsh int ipv4 set gl loopbacklargemtu=enabled

Answer 3

Just to chime in here. 24H2 for sure broke localhost connections when BRR is enabled.

Answer 4

Hello I am running Windows 11 that is the build number copied and pasted from command prompt, Afaik BBR2 is not supported on Windows 10 anyways it is only on 11.

Answer 5

Hello,

Thanks for posting to Microsoft Community!

I appreciate the detailed information you provided. However, it seems like you are currently using Windows 10, not Windows 11. To resolve the issues, you are experiencing with BBR2 congestion provider, I recommend upgrading to Windows 11 as it offers better compatibility and performance improvements. Once you have upgraded to Windows 11, you can try setting the congestion provider to BBR2 again.

When everything is resolved, feel free to mark this thread as answer and helpful. Otherwise, please let me know if there's anything else I can help you with.

Best Regards, Van Johnson | Microsoft Community Moderator