How DNS Works
DNS (Domain Name Services) are not the enigma many new users see them as. Once the process is explained most users will understand how the service works and how to troubleshoot problems. So to start you on your path to understanding DNS we'll start from the very beginning.
DNS deals with domains. Domains come in many forms and maintain a hierarchical structure. The top level domains (TLD) are maintained by ICANN (Internet Corporation for Assigned Names and Numbers). These TLDs come in forms such as .com, .org, .net and many many more. So in laymans terms the TLD is the portion of the domain name to the far right after the right most ".".
The Second Level Domain portion of a domain name to the left of the TLD and is maintained by the domain owner. In order to become the domain owner you must register the domain with a registrar. Once you are the owner of the domain you can manage the DNS records which belong to the domain. These records can be hosted on any DNS server whether the server belongs to your registrar, your ISP, your hosting provider or even yourself.
The last level of the hierarchy we will discuss here is the host name/sub-domain. At times these terms are used interchangebly but these can serve differnet purposes. The third set of characters from the left is the host record. For example in "myhost.mydomain.com" the "myhost" text portion is the host name. This portion normally provides the data for a single computer or website.
For the purposes of this article we will discuss hosting your DNS domain on your own DNS server. there are several types of DNS records you need to be aware of in order to start this process.
- A Records
- NS Records
- MX Records
- CNAME Records
- TXT records
- PTR records
An A Record is the most common type of DNS record and basically it point a name to an IP. This allows a user to type in a recognizable name and the DNS process will convert the user friedly name into an address the clinet computer can use to reach the destination host.
An NS Record directs a client to the DNS server that hosts the DNS records for the domain. NS records must be a hostname not an IP address. The hostname must refer to a valid A record and cannot refer to a CNAME record.
***Some of the confusion regarding DNS stems from this record. The TLD maintainer will also have NS records for your domain on the TLD DNS servers. Creating these records is called "registering your DNS server with your registrar". This registration occurs via your registrar and the registrar should have a control panel that allows you to create NS records with them. These NS records will traditionally match the NS records you host on your own server for the domain.
***Two NS records can not have the same IP addresses. This means that you cannot have multiple TLD NS records for the same IP address. However, you can have a unique NS record for each IP address you have on the server. Additionally you can use a single NS record to host multiple domains.
MX Records direct a query to the mail server thatis responsible to accept inbound email for your domain.
CNAME Records refer additional hostnames to an A record.
TXT Records are used for purposes like SPF (Sender Policy Framework) records used for email verification.
PTR Records are Pointer records used in rDNS (reverse DNS).
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