Bridging

What this chapter covers

Bridging joins interfaces into one Layer 2 network, and this chapter shows how to do it on RouterOS.

It covers what a bridge is, how to create one and add ports, and which bridge settings matter. It then covers the special problem of bridging across a wireless link and how station bridge mode solves it.

A bridge is the usual way to build a LAN on a MikroTik router. The default configuration of many devices already contains one, so you meet it on your first day.

How the topics fit together

The wired bridge is the base, and the wireless case builds on it.

First you learn the bridge itself. A bridge is a virtual interface that holds ports, learns MAC addresses and carries the IP address of the network.

Then you extend that bridge over a wireless link. A plain wireless station cannot be bridged, so the station bridge mode lets the remote wired hosts join the same Layer 2 network.

The key ideas to carry from page to page are these:

• Bridged ports share one broadcast domain and one subnet.
• The IP address, DHCP server and firewall rules attach to the bridge interface.
• The WAN port stays outside the LAN bridge.
• A wireless station needs a special mode before it can be bridged.

How to use these pages

Each topic page has the same shape, so you can skim for what you need.

• What it is: the idea in plain words.
• How it works: the mechanism, with diagrams and console examples.
• What to remember for the exam: the facts to memorise.
• Common mistakes: the classic traps.
• Check yourself: three questions to test your understanding.

Try the bridge steps on a router with a few free ports. For the wireless page, two RouterOS wireless devices make the exercise much easier to follow.