CompTIA Network+ Practice Test

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What command is used for reverse lookups in DNS?

nslookup
dig -x
whois
ping

The correct answer is: dig -x

The command that is used for reverse lookups in DNS is indeed "dig -x." This command is specifically designed to perform a reverse DNS lookup, allowing you to query the Domain Name System to find the domain name associated with a given IP address. When you use "dig" with the "-x" option followed by an IP address, the process involves sending a request to the DNS server to retrieve the PTR (Pointer) record. This record maps an IP address to a hostname, effectively reversing the usual forward lookup process, which translates hostnames to IP addresses. In contrast, while "nslookup" can also perform reverse lookups, it is not exclusively focused on this function, and the "-x" flag in the "dig" command makes it clear what type of query is being executed. The "whois" command is used for querying databases about domain registration details, while "ping" is a utility that simply checks the reachability of a host and measures round-trip time without performing DNS lookups. These functionalities highlight why "dig -x" is the most appropriate command for reverse lookups in DNS.