# How DNS Resolution Works ## **What is DNS and why name resolution exists** ### **DNS** * DNS Means Domain Name System * It is like an internet phone book, used to translate human friendly domain names to machine readable ip address like `192.168.32.72` * It is a distributed network of servers (root, TLD and authoritative) that work together to find the correct IP address of a domain ### **Root vs TLD vs Authoritative servers** * **Root Server:** This is the highest level in the DNS hierarchy represented by the dot (.), which knows where to find the servers for all TLDs (like .com, .org) * **Authoritative Server:** Holds the actual DNS records (like IP address) for a specific domain and provides the definitive answer(IP address) to a query * **TLD Server:** Manages specific domain extensions like (.com, .net, .uk) and directs queries to the correct authoritative servers for domains with in that extension ![](https://substackcdn.com/image/fetch/$s_!P_Ol!,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Ff0a1bb2c-a1bc-40ce-abde-6fb9d2a66ce8_1600x570.png align="left") ### **Why Name resolution exists** * **Usability:** Humans remember names, not numbers, DNS allows you to use `www.amazon.com` instead of string of numbers * **Scalability:** As the internet grew, a manual system of the text become unmanageable, DNS provides a standardised, distributed solution for a massive network * **Efficiency:** it uses caching to store frequently used address locally, to reduce network load for future requests * **Foundation of Internet:** without it, accessing websites, emails and online services would be incredibly difficult as you need to know the IP address of every server. ## **What is the dig command and when it is used** * `dig` (Domain Information Groper) * It retrieves information about the DNS Servers. * Mostly network administrators use it to verify and troubleshoot DNS problems and perform DNS lookups. ### `dig google.com` Performs a standard lookup for google.com ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1769262025129/e8ee6cd8-fc7e-44b0-96d9-b6326ec9d664.jpeg align="center") `dig google.com +short` Provides a concise answer, showing the IP address ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1769262041387/d597ace2-82d9-4807-8ac5-bccf58154d82.jpeg align="center") `dig google.com MX` Queries for mail exchange (MX) records ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1769262230040/35770982-560d-4881-9aaf-39d3903324a0.jpeg align="center") `dig @8.8.8.8 google.com` Queries google’s public DNS server directly ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1769262171729/1a5a633a-fa99-4b42-872d-676ebd4f5e86.jpeg align="center") ## **Understanding dig . NS and root name servers** ### Root Name Servers * These are authoritative DNS Servers that serve at the top level of DNS hierarchy * They do not know the IP address of `www.google.com` but they know which top level domain (TLD) servers handle specific extensions like `.com`, `.org`, `.in` * There are only 13 root name servers all over the world. * While there are 13 IP addresses, there are hundreds of physical servers worldwide using Anycast routing to ensure fast, reliable responses. ### NS * NS means Name Server, a fundamental type of DNS record that identifies which DNS servers are authoritative for a domain * It specifies which server is in-charge of managing the DNS zone file for a domain * It enables the delegation of a domain to specific DNS provider like cloud-flare, AWS, GoDaddy ### Why NS Records Matter? * NS Records are essential for the proper functioning of the internet, without them users can not access websites and emails * **Website Accessibility:** NS records tell browsers where to find the IP address * **Redundancy and Reliability:** it’s a best practice to have multiple NS records (primary, secondary).  If one NS fails, the other can takeover and resulting no down time ### `dig .NS` * `dig`**:** Domain information groper * `dot(.)`: Represents the root zone of the DNS hierarchy * `NS`**:** to list the authoritative name servers which are responsible for root zone. * You will see the list of 13 root server names ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1769262463834/1b1c492e-ad73-4d8a-867f-cc99c15696a5.jpeg align="center") ## **Understanding** `dig com NS` **and TLD name servers** This is used to query the authoritative name servers responsible for the top-level domains (TLD’s) ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1769262508655/e687c169-cb5b-4ed7-90a8-dad25d9e9537.jpeg align="center") ## **Understanding** `dig google.com NS` This looks up the name servers for a specific domain `google.com` ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1769262605205/dc3de7aa-7dad-4f56-8c1b-3402520478ab.jpeg align="center") ## **Understanding** `dig google.com` **and the full DNS resolution flow** * If you request `google.com` in browser, then it will check in cache, if not found then it will ask for other root name servers * Then Root name servers will says, I do not know `google.com` but you can ask for `.com` TLDs * Then request goes to TLD servers where you will get the response with the addresses of authoritative name servers (eg: `ns1.google.com`, `ns2.google.com`) * Then the query goes to authoritative name servers, this server holds the actual DNS records for `google.com` (A record) * Then Recursive resolver receives the IP, caches it and return the data * Then your device receives the IP and your browser connects to that IP. ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1769262747621/6e929411-1713-4e5e-b309-928b5c299d8a.jpeg align="center") ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1769262784588/515c4793-6fe6-4b1d-892d-2d147fcf9e1d.webp align="center")