DNS – An Introduction

DNS or the “Domain Name System” is the largest distributed database in the world today. It is a directory service for the internet that converts memorable hostnames such as http://www.letshost.ie/ into IP addresses which networking equipment use for directing/routing requests for information. Without DNS, the Internet as we know it would not function.

Example of DNS in practise:

A home user’s PC will query its ISP’s (Eircom broadband, Smart telecom etc) cache of a DNS record when trying to access an online resource such as a website. If the ISP has a cached record of a domain name it will provide the result to the requesting PC (through an internet browser for example) and from there the online resource will be located and presented.

If you have changed DNS on a domain recently (typically when transferring hosts) this cache may be outdated and can take up to 24 hours to update. This scenario is when most people will encounter DNS for the first time (unfortunately in an often negative light!)

DNS records are made up of various components but the most widely known elements are:

• A record: This maps a hostname to a 32bit IPv4 address
• AAA record: This maps a hostname to a 128bit IPv6 address (this is becoming more popular as we run out of IPv4 addresses and move towards IPv6)
• MX record: A mail exchange record – this maps mail servers for a domain name
• TXT record: A record reserved for human readable text which is used mostly for the Sender Policy Framework (SPF)

At LetsHost, we can take care of all DNS matters for you such that you should never have to worry about their configuration, but we do provide free facilities to manage your name servers and the DNS zone file if required. If you have any queries on your DNS records or DNS setup please open a ticket with our support department and we can assist further.