DNS records


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DNS records

A DNS server is configured with a "zone file" for each domain that contains "resource records." There are several types of records, and the most common are described below. See DNS.

Forward DNS and Reverse DNS (A and PTR)
The Address (A) record associates a domain name with an IP address, which is the primary purpose of the DNS system. The Pointer (PTR) record provides data for reverse DNS, which is used for logging the domain name and verification purposes. Also called "inverse DNS," the PTR record is an option. See reverse DNS.

Aliasing Names (CNAME)
The Canonical Name (CNAME) record is used to create aliases that point to other names. It is commonly used to map WWW, FTP and MAIL subdomains to a domain name; for example, a CNAME record can associate the subdomain FTP.COMPUTERLANGUAGE.COM with COMPUTERLANGUAGE.COM.

DNS Name Servers (NS)
The Name Server (NS) record identifies the authoritative DNS servers for a domain. A second name server is required for redundancy, and two NS records must be in the zone file (one for the primary; one for the secondary). The secondary server queries the primary server for changes.

Mail Servers (MX)
The Mail Exchange (MX) record identifies the server to which email is directed. It also contains a priority field so that mail can be directed to multiple servers in a prescribed order.

Text Record (TXT)
A TXT record can be used for any kind of documentation. It is also used to provide information to the SPF email authentication system. See SPF.

First Record in File (SOA)
Start of Authority (SOA) is the first record in the zone file. It contains the name of the primary DNS server, which must correspond to an NS record in the file, the administrator's email address and the length of time records can be cached before going back to the authoritative DNS server.

The SOA also includes data for the secondary DNS server such as the date of last update (the "Serial Number") and time intervals for checking the domain.
SUMMARY OF COMMON ZONE FILE RECORDSRecord Name (purpose) Associate This to ThatSOA record (1st record)

 TXT record (documentation)

 CNAME record (aliases)
  associate an alias to a domain

 DNAME record (aliases)
  associate an alias to a subdomain

 MX record (mail server)
  associate mail to a mail server

 NS record (authoritative server)
  associate a domain to a DNS server

 A record (forward DNS - IPv4)
  associate subdomain to 32-bit IP

 AAAA record (forward DNS - IPv6)
  (1st IPv6 record)
  associate subdomain to 128-bit IP

 A6 record (forward DNS - IPv6)
  (future IPv6 record)
  associate subdomain to 128-bit IP

 PTR record (reverse DNS)
  associate IP address to a subdomain
References in periodicals archive ?
DNS records work like a telephone book, converting human-readable website names like example.
The benefit of this approach is that owners of mail domains can independently register their own authorized IP addresses in DNS free of charge, and recipients of e-mail messages can perform queries of DNS records for SPF entries free of charge.
The idea is that organizations create their own key pair and publish the public key in their DNS records.
Ensure the provision of data lines and circuits, including services linked to them and to provide public IP addresses, DNS records management and on-line access to management and overview of the state.
Syrian Electronic Army attacked Qatar platform on October 19, 2013, and changed the DNS records of many government, private and military websites for about a day.
It appears that our account used to manage the DNS records registered at Network Solutions has received a fake password-reset request which was honored by the provider," the company wrote on its blog.
DNS Backup - Backup and restore DNS records from and to text files (no need for System State).
lt;p>Speculation is mounting that Baidu's web servers weren't actually hacked themselves, but instead its DNS records were compromised.
The aliased domain gets all the subdomains and DNS records of the original.
These systems call for email senders to publish the IP addresses of their outgoing mail servers in their DNS records.