DNS Basics

DNS Basics




The DNS (Domain Name system) is employed in networks because, while computers use numbers, it is easier for people to remember names. It’s more difficult for people to remember 209.85.171.100 than to remember “Google.com”.

DNS makes the IP numbers more human-readable by translating them into words, and vice versa (like a telephone book). DNS servers accomplish this task by having an different set of “records”. Following is a list of the records you’ll find most useful. There are other types of records such as TXT records, but they’re not necessary for the majority of applications.

The IP address(es) that the website can be located on is on the “A” (great number) record. An example of an IP address is 123.45.678.9. Every network is identified by a specific IP address.

The inverse of A records, PTR (Pointer) records are employed by Reverse Map zone files to match a great number name with an IP address.

A mail exchanger or MX record is a sort of resource record in the Domain Name System which specifies how Internet e-mail needs to be routed. MX records have two parts: a preference, and a great number name. An MX record may have a form such as mydomain.tld 14000 (10) mydomain.tld. It’s possible to have multiple MX records for one great number.

A CNAME – Shorthand for canonical name, also called a CNAME record, a record within a DNS zone which specifies the true, or canonical great number name of a computer with which its aliases are associated. An IP address is necessary for a computer hosting Web site to connect to the World Wide Web. While the IP address is generated by the DNS from its domain name, oftentimes an IP address will be produced by multiple domain names, in which case the CNAME will need to be employed. There’s no limit on the number of CNAME aliases a machine can have, but the database must contain a separate CNAME record for each one of them. A CNAME record is most commonly used to accept “www.”, when the domain is typed in by someone.

NS (Nameserver) Records – NS records list the allowable name servers in the domain. An elementary DNS zone is shown, below:

  • sampledomain.org. 86400 IN NS ns1.samplehostname.com.
  • sampledomain.org. 86400 IN NS ns2.samplehostname.com. (Domains are required to have at the minimum two NS records)
  • customers 14400 IN A 569.20.67.199 (This is a subdomain “A” record – it would look like customers.sampledomain.org when typed into your browser)
  • sampledomain.org. 14400 IN A 569.20.67.199
  • mail.sampledomain.org. 14400 IN A 569.20.67.199
  • webmail.sampledomain.org. 14400 IN A 569.20.67.199
  • ftp.sampledomain.org. 14400 IN CNAME sampledomain.org.
  • www.sampledomain.org. 14400 CNAME sampledomain.org.
  • sampledomain.org. 14400 MX (10) mail.sampledomain.org.

The rest of the entries in DNS zone records:

TTL – 14400 and 86400 – TTL “Time to Live” specifies the time period, in seconds, within which client side programs may cache the record. The records should be cached if it is set at 0. 0 to 2147483647, or 68 years, is the range that will be defined.

Class – IN – The class indicates the record kind. Internet is also called IN. Every other option is outdated. You must use “IN” if your DNS is on the Internet or Intranet.




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