IP Address Forward and Reverse Lookup

DNS and Other IP Lookup Methods

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IP address lookup refers to the process of translating between IP addresses and internet domain names. Forward IP address lookup converts an internet name to an IP address. Reverse IP address lookup converts the IP number to the name.

Why Are There IP Addresses and Names?

Because an IP address is a lengthy string of numbers, it would be difficult for a computer user to remember, and it would be susceptible to typographical errors.

Instead, computer users enter URLs to go to websites. The URLs are easier to remember and less likely to contain typographical errors. However, those URLs must be translated to the corresponding lengthy numerical IP addresses in order for the computer to know where to go.

Lookup Services

Several internet services support both forward and reverse IP lookup for public addresses. On the internet, these services rely on the Domain Name System and are known as DNS lookup and reverse DNS lookup services.

On a school or corporate local area network, private IP address lookups are also possible. These networks use internal name servers that perform the comparable functions to DNS servers on the internet. In addition to DNS, the Windows Internet Naming Service is another technology that can be used to build IP lookup services on private networks.

About Hosts Files

Years ago, before the advent of dynamic IP addressing, many smaller business networks lacking name servers managed private IP lookups through hosts files.

Hosts files contained simple lists of static IP addresses and associated computer names. This IP lookup mechanism is still used on some Unix computer networks. It can also be used on home networks without a router and with static IP addressing in place. DHCP-based networks, like most home networks today, rely on the DHCP server to maintain hosts files.

Utility programs provided with the computer's network operating system allow IP address lookups on both private LANs and the internet. In Windows, for example, the nslookup command supports lookups via name servers and hosts files.