DNS Client and Cache

What this chapter covers

This chapter covers the DNS service built into RouterOS, which works as a client and as a caching resolver.

As a client, the router asks upstream DNS servers to translate names into addresses. As a cache, it remembers the answers and serves them to LAN hosts, so repeated lookups are quick and use less upstream traffic.

The chapter has one syllabus topic, basic configuration with static DNS entries. It is split over two pages.

How the topics fit together

The first page sets up the resolver and cache, and the second page adds your own records on top.

• Servers are the upstream resolvers that the router asks.
• Remote requests is the switch that lets LAN hosts use the router as their resolver.
• Cache keeps answers for a time, to speed up later requests.
• Static entries are records you define yourself. They answer before the cache and before any upstream server.

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 example commands.
• What to remember for the exam: the facts to memorise.
• Common mistakes: the classic traps.
• Check yourself: three questions to test your understanding.

Try each command on a lab router, then look at the effect. Note which setting you changed, and which result you expected, before you run the next test. Use /ip dns cache print to see what the router has remembered, and test static entries from a LAN host with a lookup tool.

Checking each change straight away is the best way to learn how the pieces interact. The DHCP chapter links back to this one, because a DHCP server can hand out the router as the DNS server for its clients.