How to Enable BBR on Ubuntu 25.10

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BBR (Bottleneck Bandwidth and RTT) is a modern TCP congestion control algorithm developed by Google. It helps improve network performance by optimizing bandwidth usage, reducing latency, and minimizing packet loss.
By default, Linux systems use older congestion control algorithms such as Reno or CUBIC, but switching to BBR can significantly improve throughput and stability for servers and desktops.

This guide will show you how to enable BBR on Ubuntu 25.10.

Check Available Congestion Control Algorithms

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Run the following command to check which TCP congestion control algorithms are available on your system:

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

Next, check which congestion control algorithm is currently being used:

sysctl net.ipv4.tcp_congestion_control

Output:

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

Enable TCP BBR

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Open the sysctl configuration file:

nano /etc/sysctl.conf

Add the following lines at the bottom of the file:

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

Save and close the file, then apply the changes using:

sysctl -p

Output:

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

Verify BBR Activation

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Check again to confirm that BBR is now enabled:

sysctl net.ipv4.tcp_congestion_control

Output:

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

You can also verify that BBR is active by running:

lsmod | grep bbr

Output:

root@server:~# lsmod | grep bbr
tcp_bbr                20480  0

This confirms that TCP BBR is successfully enabled and running on your Ubuntu 25.10 system.

BBR will now optimize your server’s TCP performance by improving bandwidth utilization and reducing network latency.