What are DNS root servers?
DNS root servers sit at the top of the hierarchy and serve the root zone. You might hear “there are only 13,” but it’s really 13 identifiers (A–M), each with many anycasted instances worldwide. Here’s a relaxed rundown of what they do and why the number is misleading.
Role and position 🌐
Root servers sit atop the DNS hierarchy, holding the root zone and pointing resolvers to TLD name servers (.com, .jp, etc.). A quick glossary for resolver/authoritative/DNSSEC is here.
How it works
- Recursive resolvers use root hints to query a root server; the root replies with TLD server info.
- They serve the root zone—not individual domain records.
- The root zone is signed (DNSSEC) and anchors the validation chain.
13 identifiers, not 13 boxes 🔢
A–M are just 13 labels; the actual footprint is much larger.
Why 13
- Historically, root server names were set to 13 (A.root-servers.net through M.root-servers.net).
- Each is run by a different operator (e.g., A=Verisign, B=USC-ISI, C=Cogent, J=Verisign, L=ICANN, M=WIDE, etc.).
Anycast everywhere
- Each identifier has many anycast sites; traffic goes to the nearest instance.
- Overall, there are hundreds to thousands of physical servers worldwide.
Why people say “13 servers”
- Seeing only the 13 identifiers makes it sound like 13 machines, but each has many instances.
- Early articles sometimes said “only 13,” and the phrasing stuck.
- RSSAC and the operators publish counts of anycast sites; the footprint is much larger.
Common misconceptions
It’s not a fragile set of 13 boxes; it’s globally redundant.
Myths vs. reality
- There are far more than 13 machines, so “only 13, so fragile” is incorrect.
- Multiple operators and geographic spread provide robustness.
Practical notes 💡
You don’t run root servers yourself, but knowing the basics helps troubleshooting.
Good to know
- Use `dig . NS` or `dig . DNSKEY` to view root zone data.
- Resolvers hit nearby anycast instances, so paths/latency differ by region.
- Root hints ship with DNS software; you don’t need to manage them manually in normal setups.