What Is a Bridge Network in Ubuntu 24.04?

If you’re running Ubuntu 24.04 and working with virtual machines, containers, or advanced networking setups, you’ve probably come across something called a bridge network. But what exactly is it? And why is it used?

In this post, we’ll break down what a bridge network is, how it works in Ubuntu, and when you should use one, especially in the context of home lab environments, servers, and virtualization.

What Is a Bridge Network?

A bridge network acts like a virtual Ethernet switch inside your Ubuntu system. It connects your physical network interface to other virtual interfaces, such as the ones used by virtual machines or containers.

Think of it as a “pass-through lane” from the physical network to virtual devices running on your system.

Imagine you have a physical switch (like the one on your Wi-Fi router). Now, imagine that your Ubuntu system has a virtual version of that switch, and any virtual machine or software-defined network interface can plug into it.

That’s a bridge – a software switch that connects the host network interface to one or more virtual devices.

How It Works in Ubuntu 24.04

Ubuntu 24.04 uses Netplan for network configuration. With Netplan, you can define a bridge interface and link your physical network interface (NIC), such as eno1, to a bridge (like br0).

When configured, the bridge (br0) gets the IP address, not the physical device.

For example:

network:
  version: 2
  ethernets:
    eno1: {}
  bridges:
    br0:
      interfaces: [eno1]
      dhcp4: true

In this setup:

• eno1 is handed over to the bridge
• br0 is now your primary network interface
• You can attach virtual machines or containers to br0, and they’ll be treated like full network devices on the LAN

Why Use a Bridge?

Here are the main reasons:

1. Expose VMs to the LAN

If you’re using KVM or another hypervisor, a bridge allows your virtual machines to:

• Get real IP addresses from your router (via DHCP)
• Be accessible from other devices on your network
• Behave just like physical servers

2. Advanced Container Networking

You can use a bridge for Docker or Podman containers when they need to:

• Share a network stack with the host
• Communicate with other devices outside the host

3. Better Testing Environments

If you’re testing services like DNS, DHCP, or PXE booting, a bridge is necessary so that your virtual devices can interact with the real network.

When Not to Use a Bridge

You don’t need a bridge if:

• Your VM or container doesn’t need to talk to other LAN devices
• You’re fine with NAT (Network Address Translation) behind the host
• You’re trying to isolate traffic for testing or development

In those cases, a default NAT setup (like what libvirt provides out of the box) may be better.

Summary

A bridge network in Ubuntu 24.04 is a powerful tool for connecting virtual or software-defined interfaces directly to your physical network.

It’s ideal for:

• Virtual machines that need real IPs
• Servers or services running inside containers
• Complex network topologies in a homelab or enterprise environment

Understanding how bridges work gives you more control over how your devices, real or virtual, interact on the network.