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WHOIS : WHOIS (pronounced as the phrase "who is") is a query and response protocol that is widely used for querying databases that store the registered users or assignees of an Internet resource, such as a domain name, an IP address block or an autonomous system, but is also used for a wider range of other information. The protocol stores and delivers database content in a human-readable format. The current iteration of the WHOIS protocol was drafted by the Internet Society, and is documented in RFC 3912.

Dig : dig is a network administration command-line tool for querying the Domain Name System (DNS). Dig (Domain Information Groper) is useful for network troubleshooting and for educational purposes. It can operate based on command line option and flag arguments, or in batch mode by reading requests from an operating system file. When a specific name server is not specified in the command invocation, it uses the operating system's default resolver, usually configured in the file resolv.conf. Without any arguments it queries the DNS root zone. dig supports Internationalized domain name (IDN) queries. dig is a component of the domain name server software suite BIND. dig supersedes in functionality older tools, such as nslookup and the program host; however, the older tools are still used in complementary fashion.

Traceroute : The traceroute command attempts to trace the route an IP packet follows to an Internet host by launching UDP probe packets with a small maximum time-to-live (Max_ttl variable), then listening for an ICMP TIME_EXCEEDED response from gateways along the way. Probes are started with a Max_ttl value of one hop, which is increased one hop at a time until an ICMP PORT_UNREACHABLE message is returned. The ICMP PORT_UNREACHABLE message indicates either that the host has been located or the command has reached the maximum number of hops allowed for the trace. The traceroute command sends three probes at each Max_ttl setting to record the following:Max_ttl value, Address of the gateway, Round-trip time of each successful probe.

Nslookup : Nslookup (stands for “Name Server Lookup”) is a useful command for getting information from the DNS server. It is a network administration tool for querying the Domain Name System (DNS) to obtain domain name or IP address mapping or any other specific DNS record. It is also used to troubleshoot DNS-related problems.