What is DNS?
DNS or Domain Name System is a decentralized indexing system, used to list and identify computers connected to the internet.
Often referred to as “phone books” of the internet, they hold information that the user might query for, such as a Domain name, along with its corresponding IP address.
What is DNS Lookup and how does DNS Propagation work?
A DNS lookup, in a nutshell, is searching for the IP address of any Domain name you want.
This is done via a DNS server, when the user queries it with a domain name it returns the request with the appropriate IP address.
When these servers are updated however, it usually can take upto 72 hours for nodes worldwide to cache this new information. This is known as DNS propagation and propagation tools are used to check the progress of this process.
Related System Administrartor and Network Tools
Why does DNS propagation take so long?
DNS propagation can take between 24 to 72 hours and sometimes even longer. Generally this is caused by a few different factors, listed as follows.
TTL: TTL or Time-to-Live is the time duration set for the data to live in a network system. If the TTL set is rather high, the outdated data tends to persist in caches for a longer time period.
ISP Data Caching:
ISPs usually ask the DNS server only once when somebody requests for a certain website. This address is then cached to allow quicker loading times if other users search for the same website
Different ISPs have different DNS cache refresh rates leading to slower propagation.
Description of DNS Records types:
What is forward DNS lookup?
Using a Domain name to find its matching IP address is referred to as forward DNS lookup.
What is backward DNS lookup?
Consequently backward DNS lookup provides us the utility to use a website’s IP address to find its appropriate Domain name.
A record:
A record, or Address mapping record, stores the IPv4 address of websites with its matching Domain name.
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AAAA record:
Comparable to A records however the main difference is AAAA records are used to store IPv6 addresses with their corresponding Domain names.
MX record:
Mail Exchange records are specially designed and prioritized to handle Emails and direct them to SMTP mail servers.
CNAME record:
CNAME records are typically used to map Subdomain names to another Domain hosting. This way the DNS query process is repeated but with the Domain name instead of the subdomain..
TXT record:
TXT records allow admins to assign any text with their Domain names. This text can be anything from human readable information to anti-spam coding..
PTR record:
PTR records are reverse pointer records, their primary function being to point an IP address to its host domain. Used as a means of IP verification to solve security concerns..
NS record:
Directs the query to the authoritative Name Server, which further provides the IP of the domain designated to it.
SOA record:
Start of Authority records house vital information about a Domain or IP such as the owner's contact info, name of the primary master name server and time the domain was last updated.
