DNS Zone Essentials
Even though computers work strictly with numbers, the DNS (Domain Name system) used in computer networks uses words because humans find words easier to remember. People are more likely to remember “google.com” than a series of numbers.
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 alternative 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 at is contained on the “A” host record. An IP address is in the following format: 123.45.678.9. Every network has an IP address that is unique to it.
The opposite of A records, PTR (Pointer) records are adopted by Reverse Map zone files to tie a host name to an IP address.
A Mail exchanger record, commonly referred to as MX record, is a kind of resource record in the Domain Name System (DNS) that defines the procedure to route Internet e-mails. An MX record has a preference field and a host name field. Similar to “ydomain.tld 13000 (10) ydomain.tld”, some hosts may have multiple MX records.
A CNAME Abbreviated from canonical name and often phrased “a CNAME record”, a DNS zone record which specifies the authentic, or canonical, computer host name corresponding to its aliases. Every computer that hosts a web site needs to have an IP address, or they won’t be connected to the web. While the IP address is produced by the DNS from its domain name, once in a while an IP address will be generated by several different domain names, in which occurrence the CNAME will become a valuable tool. A website can be known by many different CNAME aliases, but each one requires a different CNAME record. A CNAME record is most commonly utilized for accepting “www.” when the domain is typed in.
NS (Nameserver) Records – NS records list the allowable name servers in the domain. Below is a sample of a very simple DNS zone.
sampledomain.org. 86400 IN NS ns1.samplehostname.com. sampledomain.org. 86400 IN NS ns2.samplehostname.com. (Each domain must have at least two NS records) customers 14400 IN A 569.20.67.199 (This is a subdomain “A” record – it would look like customers.sampledomain.org whe you type it in 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. 14400 CNAME sampledomain.org. sampledomain.org. 14400 MX (10) mail.sampledomain.org.
The DNS zone records explains the rest.
TTL – 14400 and 86400 – TTL specifies the amount of time, in seconds, “Time to Live” that client side programs may cache the record. The record should be cached if it is set at 0. 0 to 2147483647 (68 years) is the allowed range.
Class – IN – The class indicates the record type. Internet is also called IN. Every other option is outdated. You can use IN if your DNS is on the Internet or Intranet.
