The Domain Name System, contrarily termed as DNS, is a critical segment of the Internet. DNS is the analysis of a domain name to an IP address.
There are two ways to DNS lookups:
- The “normal” or forward DNS lookup and;
- The reverse DNS lookup.
Forward DNS Lookups
The forward lookup, or DNS lookup, is the most generally used approach to DNS. The bold strategy to DNS is simply finding out the IP address of a domain. People manage to find it challenging to remember long strings of numbers. Instead, it’s easier to get a domain name that uses words.
Electronic devices practise streams of 1’s and 0’s to interact. The only way for one computer to interact with another is by unique identification. The method of identification applied on the Internet is by IP addresses.
Here are the easy steps for DNS resolution:
- A user registers a domain name into an Internet browser.
- The computer transmits the domain name as a DNS call to the user’s ISP Internet Service Provider.
- The ISP resolves if it holds the IP address associated with that name;
- If not, the ISP promotes the request to other providers to determine the DNS record that contains the data.
- Once the record is located, the IP address of the domain is delivered to the user.
- Now, the user’s computer can interact directly with the server.
Many people associate DNS with a “phone book, ” the simplicity of a highly complex system. The world wide web renders the fundamental function of inter-connectivity much more than the communications relays of the past.
Reverse DNS Lookup
The levels are the same besides that it starts with an IP address and returns with the domain name in a reverse DNS lookup. In actual reality, this can take a while, and when a DNS cannot get what it needs, whether it is a domain name or an IP address, we end up with the screen we all hate that states, “this webpage cannot be found”. It is due to the servers being busy or the web browser timing out.
A Reverse DNS Lookup is simply the opposite progression of a DNS lookup. Moreover, with a standard DNS lookup, you ask the DNS or hostname to get the IP address. To explain, with a Reverse DNS Lookup, you query the IP address to get the hostname. Therefore, by accessing the IP address into the Reverse DNS Lookup Tool, you can manage the domain name linked with the corresponding IP.
For example, one IP address of Google.com is 126.96.36.199. Suppose you were to type this IP address in the Reverse DNS Lookup Tool. In that case, it will return the hostname of Google as listed in the database of the Address and Routing Parameter Area (ARPA) top-level domain of the Internet.
Why Is This Useful?
Using the tool is very helpful for a kind of purposes:
- Searching spam emails. From an IP address alone, it’s hard to distinguish legitimate mail servers from spam servers. However, specific generic rDNS names can provide clues that the mail server is spam. It is where the reverse DNS lookup arrives.
- Knowing who is visiting your website. Website visit logs usually contain IP addresses, which aren’t particularly useful for tracking exactly who is visiting your website.
- The process can be used to find the hostname of your visitors to give you a better picture of who is visiting your website. It is beneficial for those operating B2B businesses.
A DNS query for domain names when the IP address is known is called a reverse DNS lookup. Multiple domain names may be linked with an IP address. The DNS reserves IP addresses in domain names as specifically formatted titles in the pointer (PTR) records within the top-level infrastructure domain ARPA.
For IPv4, the domain is in-addr.arpa. For IPv6, the reverse lookup domain is ip6.arpa. The IP address is represented as a reverse-ordered octet representation for IPv4 and reverse-ordered nibble representation for IPv6.
When performing a reverse lookup, the DNS client converts the address into these formats before querying the name for a PTR record following the delegation chain as for any DNS query. For example, assuming the IPv4 address 188.8.131.52 is assigned to Wikimedia, it is represented as a DNS name in reverse order: 184.108.40.206.in-addr.arpa.
When the DNS resolver gets a pointer (PTR) request, it begins by querying the root servers, pointing to the servers of the American Registry for Internet Numbers (ARIN) for the 208.in-addr.ARPA zone.