How to Enable BBR on Ubuntu 25.04

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BBR stands for Bottleneck Bandwidth and RTT. It is a congestion control system that improves network performance by optimizing bandwidth utilization, reducing latency, and mitigating packet loss.
By default, Linux systems use the Reno or CUBIC congestion control algorithms.

Enabling BBR can enhance the overall web surfing and download/upload performance, especially on high-speed networks.
Let's go through the steps to enable it:

Check Available Congestion Control Algorithms

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Run the following command to check available congestion control algorithms:

sysctl net.ipv4.tcp_available_congestion_control

Output:

root@server:~# sysctl net.ipv4.tcp_available_congestion_control
net.ipv4.tcp_available_congestion_control = reno cubic

Check Current Congestion Control Algorithm

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To check which congestion control algorithm is currently active, run:

sysctl net.ipv4.tcp_congestion_control

Output:

root@ubuntu25:~# sysctl net.ipv4.tcp_congestion_control
net.ipv4.tcp_congestion_control = cubic

Enable TCP BBR

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Open the /etc/sysctl.conf file to enable BBR:

nano /etc/sysctl.conf

At the end of the file, add these two lines:

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

Save and exit the file.

Then, apply the changes by running:

sysctl -p

Output:

root@ubuntu25:~# sysctl -p
net.core.default_qdisc = fq
net.ipv4.tcp_congestion_control = bbr

Verify TCP BBR is Enabled

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To confirm that BBR is now the active congestion control algorithm, run:

sysctl net.ipv4.tcp_congestion_control

Output:

root@ubuntu25:~# sysctl net.ipv4.tcp_congestion_control
net.ipv4.tcp_congestion_control = bbr

That's it!
You have successfully enabled TCP BBR on Ubuntu 25.04, improving your server’s network throughput and latency performance.