DNS and IP Addresses: How Domain Names Work

You type "google.com" into your browser, but computers communicate using IP addresses like 142.250.185.46. DNS (Domain Name System) is the phonebook that translates human-readable names into machine-readable numbers. Without it, the internet would be unusable.

Why We Need DNS

Imagine having to remember 142.250.185.46 for Google, 151.101.1.140 for Reddit, and hundreds more IP addresses for every website you visit. It's technically possible—you can type IP addresses directly into your browser—but completely impractical.

DNS lets us use memorable names while computers use efficient numbers. It's a translation layer that makes the internet human-friendly.

How DNS Lookup Works

When you visit a website, your computer asks a DNS server "What's the IP address for this domain?" The DNS server responds with the IP, and your computer connects to that address. This happens in milliseconds, transparently.

Your ISP runs DNS servers that handle these lookups. Alternatively, you can use public DNS services like Google DNS (8.8.8.8) or Cloudflare DNS (1.1.1.1) for potentially faster or more private lookups.

The DNS Hierarchy

DNS is hierarchical. Root servers know about top-level domains (.com, .org, .uk). TLD servers know about second-level domains (google.com, reddit.com). Authoritative servers know about specific subdomains (mail.google.com, www.reddit.com).

Your DNS query cascades through this hierarchy until it finds the authoritative answer. Caching at each level speeds up subsequent lookups—your computer remembers recent lookups for hours or days.

DNS Caching and TTL

DNS responses include a TTL (Time To Live) value indicating how long the answer should be cached. A TTL of 3600 means "this answer is valid for one hour." After that, a fresh lookup is required.

Caching dramatically reduces DNS traffic and speeds up browsing. But it also means DNS changes take time to propagate—when a website moves to a new IP, some users will see the old IP until their cache expires.

DNS Security Concerns

DNS queries are typically unencrypted, meaning your ISP can see every website you visit by monitoring DNS lookups. DNS hijacking can redirect you to malicious sites by providing fake IP addresses.

DNS over HTTPS (DoH) and DNS over TLS (DoT) encrypt DNS queries, preventing eavesdropping and tampering. Modern browsers support these protocols, though they're not universally enabled by default.

Multiple IPs and Load Balancing

Large websites have multiple servers with different IPs. DNS can return different IPs for different users, distributing load across servers. This is why you and your friend might get different IPs for the same domain.

CDNs (Content Delivery Networks) use DNS to direct users to geographically nearby servers, reducing latency. When you look up netflix.com, you get an IP for a server close to you, not Netflix's main datacenter.

When DNS Fails

If DNS servers are down, websites become unreachable even though they're online. You'll see "DNS_PROBE_FINISHED_NXDOMAIN" or similar errors. The internet still works, but you can't find anything because the phonebook is offline.

This is why major DNS outages make headlines—they effectively break the internet for millions of users, even though the underlying infrastructure is fine.