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DNS Records Explained

Summary

DNS (Domain Name System) entries take a human friendly name, such as store.example.com, and translates it to an IP address. DNS can be quickly updated with some propagation time. There are a number of DNS Entries you are able to create. The following DNS Entries can be created or modified from within the DNS Zone Editor. For help see How to Modify Your DNS Records.



A Record

An A record (Address Record) points a domain or subdomain to an IP address. For example, you can use it for store.website.com or blog.website.com and point it to where you have your store. This is a common practice for people who use Amazon, eBay, Tumblr, etc.

As an example, an A Record is used to point a logical domain name, such as "google.com", to the IP address of Google's hosting server, "74.125.224.147".

These records point traffic from example.com (indicated by @) and ftp.example.com to the IP address 66.147.224.236. They also point localhost.example.com to the server that the domain is hosted on. This allows the end user to type in a human-readable domain, while the computer can continue to work with numbers.

CNAME

A CNAME (Canonical Name) points one domain or subdomain to another domain name, allowing you to update one A Record each time you make a change, regardless of how many Host Records need to resolve to that IP address.

These records point www.example.com to example.com, imap.example.com to mail.example.com, and docs.example.com to ghs.google.com. The first record allows the domain to resolve to the same server with or without the www subdomain. The second record allows you to use an alternative subdomain for email hosting an delivery. The third record allows you to use the docs.example.com subdomain with Google Apps, where you can use Google's document management system. This type of record requires additional configuration with Google.

MX Entry

An MX Entry (Mail Exchanger) directs email to a particular mail server. Like a CNAME, MX Entries must point to a domain and never point directly to an IP address.

TXT Records

A TXT (Text) record was originally intended for human-readable text. These records are dynamic and can be used for several purposes.

The TXT Value is what the record 'points to', but these records aren't used to direct any traffic. Instead they're used to provide needed information to outside sources.
The First record is used for a SPF, Sender Policy Framework, records, those records are used by many email systems to help identify if email is coming from a trusted source, helping filter out spam or messages pretending to be from your domain (called spoofing). More information on SPF records can be found at http://www.openspf.net/
The second record is used for DomainKeys, which is also used to verify that email came from a trusted source. More information on DomainKeys can be found at http://www.dkim.org/

SRV record

An SRV (Service) record points one domain to another domain name using a specific destination port. SRV records allow specific services, such as VOIP or IM, to be be directed to a separate location.

Example:

Enabling your domain to use Google's xmpp server is a good example to showcase. Google's help article states that the SRV record should be in this format:
        _xmpp-server._tcp.gmail.com. IN SRV 5 0 5269 xmpp-server.l.google.com.
        
Under "Add DNS Record", you will need to enter the settings this way:
  • Service: _xmpp-server
  • Protocol: _tcp
  • Host: chat (If you want to use the chat subdomain. Replace this with the subdomain that you want to us, or @ for the root domain.)
  • TTL: 14400
  • Type: SRV
  • Priority: 5
  • Weight: 0
  • Port: 5269
  • Points To: xmpp-server.l.google.com

AAAA Record

The AAAA record is similar to the A record, but it allows you to point the domain to an Ipv6 address. More information on IPv6 can be found at http://ipv6.com/.

DNS Glossary:

Zone File:
This is where all the DNS records are stored for a domain.
Host Record:
This is the domain or subdomain you wish to use. The @ symbol is used to indicate the root domain itself. In our example the Host Record 'ftp' would be for the subdomain ftp.google.com and '@' would be google.com itself.
Points to:
This is the destination server that the domain or subdomain is sending the traffic to.
TTL:
The 'time to live' value indicates the amount of time the record is cached by a DNS Server, such as your Internet service provider. The default (and lowest accepted) value is 14400 seconds (4 hours). You do not normally need to modify this value.
Action:
This allows you to modify or remove existing records.
Weight:
This is similar to priority, as it controls the order in which multiple records are used. Records are grouped with other records that have the same Priority value. As with MX Entries, lower numbers are used before higher numbers.
Port:
This is used by the server or computer to process traffic to specific services, ensuring that all traffic comes through the door that it's expected on.
Target:
This is the destination that the record is sending the traffic to.
Knowledgebase Article 369,589 views bookmark tags: a aaaa cname dns record srv txt zone


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