OpenDNS: the free DNS

OpenDNS (208.67.222.222 and 208.67.220.220) is a free public DNS resolver, one that appeared before the big providers’ resolvers. The principle: you replace your ISP’s DNS with theirs and your resolution goes through their servers instead of yours.

Why

Three reasons people invoke:

• The ISP’s DNS is slow, goes down, or lies (the captive portal resolving everything to its login page);
• OpenDNS filters phishing and malware domains (their malicious domain database, updated continuously);
• OpenDNS does caching and the cache is faster than the ISP’s resolver.

How

# In /etc/resolv.conf
nameserver 208.67.222.222
nameserver 208.67.220.220

Or in the network’s DHCP so every workstation benefits.

What it implies

The DNS resolver sees ALL your queries. Every name your machine asks goes through OpenDNS and OpenDNS knows which domains you visit, how often, from which source IP. It is a trusted third party and the “trust” in “trusted third party” is meant strongly: you give them the complete history of your DNS navigation.

OpenDNS does filtering (malicious domains redirect to a “blocked” page), which means they DECIDE what you can visit. The filtering is configurable (can be disabled), but the default enables it and the default is the behavior 95% of users never change.

What it is worth

For the sysadmin managing a fleet: OpenDNS is a fallback resolver (the ISP’s DNS goes down, OpenDNS takes over). For the individual: filtering is a plus, but the trusted third party is a cost. The lesson fits in one sentence: the public resolver is fast, free and it sees everything.

[edit: 2026] OpenDNS became Cisco OpenDNS (acquired 2015), Google Public DNS (8.8.8.8) and Cloudflare (1.1.1.1) took the market and the trusted-third-party vs ISP vs self-hosted debate is the same. The DNS-inventory lesson applies: your DNS is your inventory and if your resolver is a third party, your inventory belongs to that third party.