DNS Root Server

DNS root servers sit at the top of the hierarchy and know where to find the authoritative nameservers for every top-level domain. They do not hold records for ordinary domains; they reply with a referral to the right TLD servers.

Why it matters

Every resolver starts from a built-in list of root server addresses (the root hints) when its cache is empty. There are 13 named root server identities, letters A to M, run by a dozen independent organizations. Each identity is actually served by many machines at hundreds of locations through anycast, so there are far more physical servers than names. The root zone is signed with DNSSEC, which anchors validation for the whole tree.

Example

Asking a root server about a domain returns a referral, not an answer:

$ dig +norecurse @a.root-servers.net example.com NS
;; AUTHORITY SECTION:
com.   172800 IN NS a.gtld-servers.net.
com.   172800 IN NS b.gtld-servers.net.

The resolver then asks a .com server, which refers it to the domain's own nameservers.

Common mistakes

• Believing the internet depends on only 13 machines.
• Thinking resolvers query the root for every lookup. Referrals are cached for a long time.
• Mixing up the root zone with the registry zones below it.

Related

• TLD
• Anycast
• DNS resolver
• DNSSEC

यह पेज सामान्य जानकारी है, जिसे हमारी संपादकीय टीम ने लिखा है और दस्तावेज़ीकरण बदलने पर अपडेट किया जाता है। सर्वर और प्रदाता अलग-अलग होते हैं, इसलिए बदलाव पहले सुरक्षित तरीके से जाँचें। देखें: संपादकीय नीति और अस्वीकरण.