That failure may occur within the company's private network or the internet. What is DNS failure?ĭNS failure means that the DNS server cannot convert the domain name into an IP address in a TCP/IP network. That is true when DNSSEC is used, which adds extra overhead to the DNS query packet. TCP 53 is used primarily for Zone Transfers and when the query packet exceeds 512 bytes. Be sure, when using the UDP 53 for DNS, the maximum size of the query packet is 512 bytes. That is used when the client's computer communicates with the DNS server for resolving the specific domain name. However, the most frequently used port for DNS is UDP 53. What is the port used by DNS?ĭNS uses both TCP and UDP port 53. The DNS server will return a name error, also known as an NXDomain response (for non-existent domain), to symbolize that the query's domain name does not exist. What will happen if the domain name does not exist? That information is temporarily cached, and DNS servers will go for the updated DNS information when TTL (Time to Live) expires. The DNS client or the server may cache the information the DNS records in its DNS cache. The ISPs across the world have a different caching level. Geolocation involves in mapping IP address to the country, region (city), latitude/longitude, ISP and domain name among other useful things.
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