权威DNS服务器

The Authority Hierarchy

The DNSDomain Name System. The hierarchical, distributed naming system that translates human-readable domain names (e.g., example.com) into IP addresses (e.g., 93.184.216.34). Often called the "phonebook of the internet." namespace is a tree, and authority is delegated downward. IANA delegates top-level domain (TLD) zones (.com, .org, .uk) to TLD registries. TLD registries delegate individual domains to registrants' chosen name servers via NS RecordName Server record. A DNS record that delegates a domain or subdomain to a set of authoritative DNS servers. Every domain must have at least two NS records for redundancy.s. Those name servers are the authoritative DNS servers for the domain — they hold the definitive copies of all records: A RecordA DNS record that maps a domain name to an IPv4 address (e.g., example.com -> 93.184.216.34). The most fundamental DNS record type for resolving domain names to IP addresses., AAAA RecordA DNS record that maps a domain name to an IPv6 address. Named "AAAA" (quad-A) because an IPv6 address is four times the size of an IPv4 address., MX RecordMail Exchange record. A DNS record that specifies the mail server responsible for receiving email for a domain, along with a priority value that determines the order in which servers are tried., CNAME RecordA DNS record that creates an alias from one domain name to another (e.g., www.example.com -> example.com). The alias inherits all DNS records of the target, but cannot coexist with other record types at the same name., TXT, SOA, and more.

When a DNS ResolverA server that receives DNS queries from clients and resolves domain names by querying the DNS hierarchy on their behalf. Public resolvers like 1.1.1.1 (Cloudflare) and 8.8.8.8 (Google) are widely used alternatives to ISP resolvers. needs to resolve www.example.com, it starts at the root servers, follows NS referrals down the hierarchy (root to .com to example.com), and finally queries the authoritative server, which answers definitively.

Primary and Secondary Authoritative Servers

Authoritative zones are typically served by multiple servers for redundancy. The primary server holds the master copy of the zone file; secondary servers receive zone transfers (AXFR or IXFR) from the primary and serve read-only copies. NS RecordName Server record. A DNS record that delegates a domain or subdomain to a set of authoritative DNS servers. Every domain must have at least two NS records for redundancy.s published in the TLD zone list all authoritative servers for a domain — at least two are required by most registrars.

Authoritative vs. Recursive DNS

The distinction matters for troubleshooting. A DNS ResolverA server that receives DNS queries from clients and resolves domain names by querying the DNS hierarchy on their behalf. Public resolvers like 1.1.1.1 (Cloudflare) and 8.8.8.8 (Google) are widely used alternatives to ISP resolvers. (recursive resolver) answers client queries by querying other servers on the client's behalf and caching results. An authoritative server answers only for zones it's configured to serve and does not recurse. Mixing the two on the same server (common in early internet infrastructure) creates security risks — authoritative servers that also recurse are vulnerable to cache poisoning attacks.

Use DNS Lookup to query authoritative servers directly, bypassing cached results from recursive resolvers.