Steps to check and enable BBR in Linux system

The steps to check and enable BBR in Linux system are as follows:

Check if BBR is enabled

1. View the current congestion control algorithm :

   bash

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   sysctl net.ipv4.tcp_congestion_control

   If the output is net.ipv4.tcp_congestion_control = bbr, it means BBR is enabled.

2. Check queue discipline (qdisc) settings :

   bash

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   sysctl net.core.default_qdisc

   When BBR is enabled, it is usually set to fq.

3. Verify whether the kernel module is loaded :

   bash

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   lsmod | grep bbr

   If the output contains the tcp_bbr module, it means it has been loaded.

If BBR is not enabled, the steps to enable it are as follows:

1. Confirm kernel version (requires ≥4.9):

   bash

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   uname -r

2. Edit sysctl configuration :

   bash

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   sudo nano /etc/sysctl.conf

   At the end of the file add:

   conf

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   net.core.default_qdisc = fq
   net.ipv4.tcp_congestion_control = bbr

3. Application Configuration :

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   sudo sysctl -p

4. Confirmed and effective :

   bash

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   sysctl net.ipv4.tcp_congestion_control # should output "bbr"
   sysctl net.core.default_qdisc # should output "fq"

Other notes

• Permission issues: Use sudo to execute the command to ensure sufficient permissions.

• The kernel does not support : If the kernel version is too low, you need to upgrade the kernel (such as Ubuntu/Debian using TAGP H20linux-generic-hwe package, CentOS uses the ELRepo repository).

• Manually load module (rarely required):

  bash

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  sudo modprobe tcp_bbr

After completing the above steps, BBR will take effect to improve network performance.