Knowledgebase: DNS
What are DNS records
Posted by Chris Atherton on 17 July 2012 12:09 PM

DNS records come in many forms however before explaining what the records do and how they work please have a look over our article on what DNS is, if you are not familiar with it:

 

http://www.ehosting.com/support/index.php?/Knowledgebase/Article/View/76/40/what-is-dns

 

Now that you are aware of the concept of DNS let’s look at more detail into the nuts and bolts; DNS records.  Going back to the phone book analogy; DNS records are the equivalent of the phone extensions for your domain. There are a number of different DNS records but there are 4 common types of DNS records which you will encounter:

 

A record – Points to an IP address.

CNAME record – Points to an A record

NS record – points to an A record for nameserver information.

MX record – Points to an A record for emails.

 

Each record performs a specific function, however all records simply exist to point to an IP address, another DNS record or provide information on the domain.

 

Let’s first have a look at the most useful DNS record; the A record:

 

Record                  Type           TTL                     Priority             Content

ehosting.com         A                10 minutes                                  91.102.64.36

www.ehosting.com A                 10 minutes                                  91.102.64.36

 

All ‘A’ records will point to the IP address. This is the computer address where you are telling computers to look for your website content or email service.  The above is an example of the contents of a DNS zone (the contents on the nameserver for your domain).  As you can see the record name is the domain (or sub-domain), in other words this will be what you are searching for when you enter this into a web browser.  Then you have the record type, A in this case.  Next is the ‘time to live’, so every 10 minutes the DNS should be updated, the priority is blank because it is not a value attributed to A records and finally the content, in other words the destination.

 

After the A record the most common is the CNAME record.  This will point the domain you are looking for to an A record.  It will not redirect the site contents; rather it will direct you to where the content is stored.  For example:

 

Record                  Type           TTL                     Priority             Content

www.ehosting.com CNAME        10 minutes                                  ehosting.com

ehosting.com         A                10 minutes                                  91.102.64.36

 

As you can see from above when searching for www.ehosting.com DNS will return the IP address for the A record ehosting.com.

 

The next most important record is the MX record.  This is a special type of record that only deals with email.  When an email server wants to send an email to your domain it will look up the mx record for your domain on the nameserver your domain is using.

 

Record                  Type           TTL                  Priority                Content

ehosting.com         MX              10 minutes            10          mail. ehosting.com

mail.ehosting.com A                10 minutes                                  91.102.64.36

 

Looking at the example above you will notice that there is a priority set on the mx record.  The lower the number, the higher the priority.  This can be useful, for example if a particular mail server at 91.102.64.36 was not available for some reason a backup mail server can be used.  For most people only the one mail server is necessary.

That leaves us with only the NS records remaining to be covered.  NS records list the nameservers where your domains DNS information is stored.  These records need to match the DNS records that you have set with your registrar.  If they don’t errors will start to occur with the DNS not being found.

 

For more information on DNS and what each DNS record type does please see the following link:

 

http://en.wikipedia.org/wiki/List_of_DNS_record_types


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