Information about a domain is stored in DNS records, also sometimes known as zone files. The DNS records are stored on DNS name servers. For each domain, there are at least two authoritative DNS name servers, where the authoritative DNS record for that domain is stored. Other name servers in the domain name system will regularly download a copy of that DNS record from the authoritative source to make sure their record is up to date. You, or an authorised third party set the addresses to the authoritative DNS name servers when you register your domain with a domain name registrar.
Editing DNS Records
DNS records can and should be edited by the owner of a domain, or someone authorised by the owner – it will be necessary at least once when you first setup hosting for your website. DNS records are edited in an interface connected to the domain’s authoritative name servers. Many domain name registrars also provide name servers and allow you to edit DNS records when logging into the registrar’s member’s area. If not, you will need to login to the member’s area of the company hosting the name server and edit DNS records there. When you commission us to build a website, it is highly likely we will request login access to the DNS editing area for your domain.
When you edit the DNS records at the authoritative name servers, it will take several hours for the other DNS name servers on the internet to download the changes. This process is called DNS propagation. Until propagation is complete, some web surfers will receive old DNS information from their DNS server. So if you are moving hosts for your website and have changed the primary IP address to suit, some visitors will be taken to your old website for up to a day or two after making the change to the DNS record. It is therefore a good idea to leave your old host switched on for a day or two after changing DNS records to provide visitors a seamless transition.
DNS Record Types
The most important information in a domain’s DNS record is the primary IP address which corresponds with the domain. This record is called an
(A) record. When you visit a website for that domain in your browser, this IP address is what is provided by the DNS servers. The DNS record can also contain IP addresses for an email server in an entry called an
(MX) record. This works in a similar way to visiting a website but rather than your browser requesting an
(A) record, your email program requests the
(MX) record when sending an email to someone on that domain.
There are several other types of entries in the DNS record and each one has a specific purpose. Not all are necessary, but all are useful. Some entry types are used by the domain name system to keep the entry up to date across all DNS servers.
Read more about DNS Records at the Wikipedia list of DNS record types. Read more about how the DNS system works at How Stuff Works and Net Registry.