What is bridge?

A bridge is a networking device (or software function) that links two separate network segments so they can communicate as if they were one larger network. It looks at each data packet, checks the destination’s hardware address, and decides whether to forward the packet to the other segment or keep it on the current one.

Let's break it down

  • Network segment: a group of devices that share the same physical connection (like a wired Ethernet cable).
  • MAC address: a unique identifier built into every network card; bridges use it to know where a device lives.
  • Learning: when a bridge receives a packet, it records the source MAC address and the port it came from, building a small table.
  • Filtering: if the destination MAC is already known to be on the same side, the bridge blocks the packet, preventing unnecessary traffic.
  • Forwarding: if the destination is on the other side, the bridge sends the packet across the link that connects the two segments.

Why does it matter?

Bridges help expand a network without creating a single, overloaded broadcast domain. They reduce unnecessary traffic, improve performance, and allow older or different types of network media (like wired and wireless) to work together seamlessly.

Where is it used?

  • Home routers that offer a “bridge mode” to connect a separate Wi‑Fi system.
  • Office LANs where a wired floor and a wireless floor need to share resources.
  • Industrial settings linking legacy Ethernet lines to modern switches.
  • Virtual environments where software bridges connect virtual machines to the physical network.

Good things about it

  • Simple to set up and often works automatically (plug‑and‑play).
  • Transparent to users; devices don’t need to know a bridge exists.
  • Improves network efficiency by limiting broadcast traffic.
  • Inexpensive compared to full‑blown routers for basic segment linking.

Not-so-good things

  • Only works at the data‑link layer; it can’t route traffic between different IP subnets.
  • Limited scalability; large networks may need switches or routers instead.
  • If not managed, bridges can create loops that cause network storms.
  • Some advanced features (like VLAN tagging) may not be supported on basic bridges.