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DNS Lookup

What is DNS Lookup?

DNS lookup is a fundamental operation in internet navigation, serving as the mechanism that converts human-friendly domain names into machine-readable IP addresses. When you enter a website URL into your browser, a DNS search is performed to determine the IP address of the server where the website is housed. This method is similar to looking up a phone number in a contact book; just as you would search for a person’s name to discover their phone number, your computer will use DNS lookup to find the IP address associated with a domain.

Your device first checks to determine if it already knows the IP address by querying its local DNS cache. Your internet service provider’s (ISP) recursive DNS server is consulted if the address is not cached. In the event that the recursive server is unable to resolve the issue, it progressively contacts higher-level DNS servers, ranging from the root DNS servers to the Top-Level Domain (TLD) DNS servers (for.com,.org, and so on) and ultimately to the authoritative DNS servers that are in possession of the actual IP address record.

Reliable access to web services and speedy internet browsing depend on accurate and efficient DNS lookups. This process, which converts the names we remember into numbers that help us traverse the digital world, works behind the scenes to maintain the accessibility and usability of the huge and complex web.

How does DNS work?

Query Initiation: Your browser launches a DNS query to determine the website’s matching IP address when you enter a URL.

Check Local DNS Cache: To save query times if the IP address has been visited lately, your computer first looks up the IP address in its local DNS cache.

Recursive Resolver: Your query travels to a DNS resolver, often offered by your ISP, which will begin the process of discovering the IP address if the address isn’t in the cache.

Root Name Server: The resolver makes a request to a root name server, which responds by pointing it in the direction of the relevant Top-Level Domain (TLD) nameserver (.com,.org, etc.) for that particular website.

TLD Nameserver: By pointing the resolver to the official name server for the particular domain, the TLD name server helps to focus the search.

Authoritative Nameserver: This server gives the resolver the precise IP address associated with the domain name.

Finalised Resolution: In order for your browser to connect to the web server and load the website, the resolver provides the IP address back to your device.

How to perform a DNS lookup

A DNS lookup is simple to do and may be done in a few different ways, depending on your device and tools of choice. The basic stages for utilising standard tools to execute a DNS lookup are as follows:

On Windows:

Using nslookup:

  • Open Command Prompt.

  • Type nslookup www.example.com (replace www.example.com with the domain you’re interested in) and press Enter. This will return the IP address of the domain.

On macOS and Linux:

Using dig:

  • Open Terminal.
  • Type dig www.example.com and press Enter. This command provides detailed DNS information, including the domain’s IP address.

Using host:

  • Still in Terminal, you can also use the host command for a simpler output.
  • Type host www.example.com and press Enter. This will directly return the domain’s IP address.

DNS Record Type

A Record (Address Record)

  • Purpose: Maps a domain name to its corresponding IPv4 address (e.g., 192.0.2.1).
  • Example Usage: Directing traffic to a website hosted on an IPv4 address.

AAAA Record (Quad A Record)

  • Purpose: Think of it like the A record for IPv6 addresses.
  • Example Usage: Directing traffic to a website hosted on an IPv6 address.

CNAME Record (Canonical Name Record)

  • Purpose: connects an alias name to the canonical or real domain name. When more than one domain name resolves to the same IP address, this is used. 
  • Example Usage: Mapping a subdomain like www.example.com to the domain example.com.

MX Record (Mail Exchange Record)

  • Purpose: Specifies the mail servers responsible for receiving email on behalf of a domain.
  • Example Usage: Directing email to a domain’s email server(s).

NS Record (Name Server Record)

  • Purpose: Specifies the authoritative Name Servers for a domain, essentially telling the internet where to find information about the domain.
  • Example Usage: Delegating a specific subdomain to different DNS servers.

PTR Record (Pointer Record)

  • Purpose: The opposite of an A record, a PTR record maps an IP address to a domain name. It’s primarily used in reverse DNS lookups.
  • Example Usage: Verifying an IP address is associated with a domain name, often used in spam prevention.

SOA Record (Start of Authority Record)

  • Purpose: Gives details about a domain and its zone, such as timers, the domain serial number, the email address of the domain administrator, and the principal name server. 
  • Example Usage: Managing DNS zone transfers.

TXT Record (Text Record)

  • Purpose: Enables the addition of any text to a DNS record by the domain administrator. Often used for verification purposes.
  • Example Usage: Verifying domain ownership, implementing Sender Policy Framework (SPF) records for email, and other security measures like DMARC and DKIM.

SRV Record (Service Locator Record)

  • Purpose: Specifies the location of services like VOIP, SIP, and XMPP. It includes the hostname and port number for the service.
  • Example Usage: Directing traffic to specific service ports on servers for protocols like SIP or LDAP.

SPF Record (Sender Policy Framework)

  • Purpose: Helps prevent email spoofing by specifying which mail servers are permitted to send email on behalf of a domain.
  • Note: While SPF records were traditionally stored in their own record type, they are now typically specified within TXT records.

DNSSEC Records (DNS Security Extensions)

  • Purpose: Adds security to the DNS to protect against certain types of attacks, such as cache poisoning and DNS spoofing. Includes several record types like DS, DNSKEY, RRSIG, and NSEC.
  • Example Usage: Ensuring the integrity and authenticity of DNS responses.

 

FAQs

A DNS server converts a domain name, such as www.example.com, into an IP address that computers use to communicate with one another over the internet through a process called DNS Lookup.

Yes, you may run DNS Lookups from your computer’s terminal or command prompt using programs like ‘nslookup’ on Windows or ‘dig’ on Linux and macOS.

Online resources like DNSChecker and MXToolBox as well as command-line tools like “dig” and “nslookup” are frequently used for DNS lookups.

Yes, in an indirect way. Search engine rankings are influenced by faster page load times, which can be achieved by faster DNS Lookups.

One possible method is to utilise DNS lookup programs such as ‘nslookup’ or ‘dig’, or go to websites that let you enter a domain name and inspect its DNS records.