DNS Info
AuthorAdrian McNab Article Reference NumberAA-00615 Views5346 0 Rating/ Voters

DNS: Definition and Explanation

The Domain Name System (DNS) stores and associates many types of information with domain names, but most importantly it translates domain names (computer hostnames) to IP addresses. It also lists mail exchange servers accepting e-mail for each domain. In providing a worldwide keyword-based redirection service, DNS is an essential component of contemporary Internet use.

The technical method for keeping track of the IP addresses a domain name should be translated to is accomplished through use of DNS zone files, which store multiple one-line entries that associate a domain (or sub-domain) to an IP address. It is this DNS zone file that the DNS Management option allows you to alter as customers see fit.

For further information, we invite you to read further

Types of DNS Records

CNAME Records

A CNAME Record, also known as a Canonical Name Record or Alias Record, is used to make one domain name an alias of another domain name. For example, the default www and ftp records for most hosting accounts are CNAMEs of http://your-domain.com (the @ record). This means that www.your-domain.com, ftp.your-domain.com and your-domain.com would all point to the same location.

You can create a CNAME record in one of two ways. You can refer to an existing A Record, or you can refer to an existing Domain Name. For example:

;Zone       Server
test1       www
test2       www.other-domain.com.

The first example will result in test1.your-domain.com pointing to the same location as www.your-domain.com. The second example will result in test2.your-domain.com pointing to the same location as www.other-domain.com.

Note: Whenever you enter a fully qualified domain name in a DNS record, it must be followed by a "." or dot.

MX Records

A MX Record, or Mail Exchange Record, maps a domain name to a list of email servers. This is the part of your DNS record that tells email providers where to direct email sent to users on your domain name. If the MX record is incorrect or removed from your DNS record, you will not receive any mail to your email accounts.

You can have more than one MX Record for a domain name, but each record must list a priority. The lowest numbered MX record is respected first. Higher numbered MX records are only used if server corresponding to the lower record is unresponsive.

There are two ways you can enter a MX record, either by referring to an existing A record, or by listing the server directly in the MX record. For example:

;Zone       Server                          Priority
@           mail                            1
@           mailserver.provider.com.        5
@           168.144.#.#                     20

The first record has a priority of 1, and refers to an existing A Record called "mail". If there is no matching A Record for "mail", this MX Record would not work. The second record has a priority of 5. Since it is the second highest number, it would be respected second. This record refers to a fully qualified domain name. The third record has a priority of 20. Since it is the highest number, it would be respected last. This record refers to an IP address where a mail server is located.

Note: Whenever you enter a fully qualified domain name in a DNS record, it must be followed by a "." or dot.

NS Records

A NS Record, or Name Server Record, maps a domain name to a list of DNS servers that are authoritative for that domain name. You may notice NS Records similar to the following in your DNS Record:

;Zone       Server
@           ns3.softcomca.com.
@           ns4.softcomca.com.

These records match the Name Servers listed on your domain name WHOIS record, and list the name servers that are authoritative for your domain name. At this time, it is not possible to edit the existing NS records or add any new NS records. If you need to add an NS Records into your DNS, please contact Customer Support

A Records

An A Record, also known as an Address Record or Host Record, maps a hostname or domain name to an IP Address. This is the primary translation mechanism that translates all IP addresses on the internet to more friendly and easier to remember Domain Names.

Unlike CNAME Records or MX Records, A Records can point only to IP Addresses. You cannot create an A Record that points to a fully qualified domain name. For example:

CORRECT:

;Zone       Server
mail        168.144.#.#

INCORRECT:

;Zone       Server
test        www.other-site.com.

SRV and TXT records

At this time we do not support SRV or TXT records through our DNS management interface.

Refresh, Retry, Expire or Minimum TTL

At this time we do not support updating these settings. The default setting for all DNS records is as follows:

Refresh: 21600 seconds (6 hours)
Retry: 3600 seconds (1 hour)
Expire: 691200 seconds (8 days)
Minimum TTL: 3600 seconds (1 hour)

DNS Flush

In some cases, your computer may keep a cached copy of some DNS Records. You can execute a DNS Flush to reset the contents of the DNS resolver cache.

To Flush DNS on a Windows-based PC:

  1. Run "Command Prompt", or select Start then Run... and type: cmd
  2. Type: ipconfig /flushdns
  3. Close the Command Prompt, or type: exit

To flush DNS cache in Mac OS X:

  1. Run "Terminal"
  2. Type: lookupd-flushache
  3. Run the command

To flush the DNS cache in Linux:

  1. Restart the nscd daemon
  2. Type /etc/rc.d/ init.d/nscd restart in terminal
  3. Run the command
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