DNS
DNS is the internet's address book. When a site will not open or a change has not "propagated", DNS is usually involved. This explains how it works and how to look things up with the DNS tools in Netutilus for Mac.
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Computers connect to addresses, people type names. DNS, the Domain Name System, connects the two. Before your Mac opens example.com, it asks a resolver for the address. That’s usually your router, which asks your provider’s resolver, or a public resolver such as Cloudflare’s 1.1.1.1 or Google’s 8.8.8.8.
Records and their TTL
A domain’s DNS holds records: A and AAAA for its addresses, MX for its mail servers, TXT for text such as email security settings, CNAME for aliases, NS for the servers in charge of it.
Each answer comes with a TTL, the number of seconds a resolver may keep it before asking again. Caching makes DNS fast, and it’s also why a change can take a while to reach everyone: old answers live until their TTL runs out. DNS Propagation shows how far a change has got.
When DNS goes wrong
- The site won’t open, but the connection is fine. The name doesn’t resolve: a lapsed domain, a typo, or a broken resolver. DNS Lookup tells which.
- Everything is slow to start, then fine. Each new name takes long to resolve. Internet Check times DNS on its own and says when it’s the slow part.
- Works with one resolver, not another. Your provider’s resolver may be failing, or filtering. Try a public one in DNS Lookup.
Encrypted DNS
Ordinary DNS travels unencrypted, so anyone on the way can read which names you look up. DNS over HTTPS (DoH) sends the same questions inside an HTTPS connection. Netutilus uses it for the public resolvers in DNS Lookup and DNS Propagation.
Related
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