Domain Name System (DNS) is structure defined by Internet Engineering Task Force (IETF) which is a standard name service provider that allows your computer to register and resolve the domain names you are going to register with the hosting provider. DNS is the service which translates between Internet names and Internet addresses. The Domain Name System really and ver easily makes it possible to assign the domain names to organizations independent of the routing of the numerical IP address.
If we consider the other way round, DNS is a system that convert the domain names into IP addresses. This system is very necessary to identify as computers only make use of IP addresses yet and we human being use only human readable names since the names are easier to remember than IP addresses. DNS is a Distributed Directory Service where they Maps names to values resource records and which is the backbone of the internet and makes networks human friendly. Without this DNS resolution, the internet could be a the most difficult place to search to search around . DNS resolution is therefore a very important task. However, sometimes you try to connect to a system by name and get an error such as “DNS error” the reason behind this is the name didn’t get resolve to the proper IP address he must connect too. There could be several causes for this, such as:
# If the Domain Name System server is down.
# Internet Provider get disconnected and then the DNS cannot resolve
# DNS cache poisoning.
# Updation in the zone issues.
# The DNS server does not have network connectivity to the root servers.
There are plenty of ways to search out whether your system is resolving it in a proper way. To verify name resolution you can use nslookup to check and to resolve as well. The nslookup command can be used to find various details relating to a particular DNS (Domain Name System) such as IP address as well as the MX records etc. To check you can go to the command prompt and type the keyword “nslookup” and the host_name’s server_IP_address you got form the hosting provider. To resolve the this issue you have to replace the actual host name that you have with you with host_name and the IP address of the DNS server for server_IP_address then press enter.This will help you to verify if there is an error is in the server, if there is an error such as “widespread resolution error”, or can be the server is possibly down. Nslookup also display the variety of types of DNS records, not just primary (A) records that are there but also , or all records for a domain. You can then ping with the -a switch to also verify if DNS resolution is working fine.
Troubleshoot the dns client as most of the problems start with the failed queries at the client. If a dns server provides incorrect data to queries that it successfully answers,could be like this
# Resource records (RRs) were not dynamically updated in a zone.
# An error could be possible when adding manually or modifying the static resource records in the zone.
# Stale resource records in the DNS server database, left from cached lookups or zone records not updated with current information or removed when they are no longer needed.
If the DNS server can’t resolve the names for external networks ,there could be some more issue such as
# There could be possible if recursive query times out before it’s been completed .
# There could be possible whether the remote DNS server fails to respond.
# If the remote DNS server provides incorrect data.
# May be possible that DNS server recursion has been disabled.