Routing

What this chapter covers

Routing is how packets travel between networks, and this chapter covers the part that every MikroTik user needs.

It starts with the concepts: the routing table, connected routes, distance and route flags. It then moves to static routing, which includes the default route, dynamic routes and a worked example of two routers.

How the topics fit together

The first page explains how the router thinks, and the second page shows how you tell it what to do.

A router always starts with the connected routes that come from its own addresses. These cover the networks that are directly attached.

For every other network, the router needs more information. Static routes supply it by hand, the default route covers everything else, and dynamic sources such as a DHCP client add routes for you.

The practical rules to carry between the pages are these:

• The longest prefix match wins first, and the lowest distance breaks ties.
• A gateway must be reachable, normally through a connected network.
• Both directions of a conversation need a route.
• The flags tell you whether a route is active, dynamic, connected or static.

The two pages are meant to be read in order. The concepts page gives you the vocabulary, and the static routing page puts it to work on a small network that you can rebuild in a lab.

Routing questions in the exam often come down to one of three checks. Is there a route, is it active, and does a route exist for the return path?

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.

Read /ip route print on a real router and decode the flags before you read the second page. Then build the two router example in a lab, and break it on purpose by removing one return route.