Domain Internet Groper (DIG) is a flexible tool for interrogating DNS name servers. It performs DNS lookups and displays the answers that are returned from the name server(s) that were queried. Most DNS administrators use dig to troubleshoot DNS problems because of its flexibility, ease of use and clarity of output. Other lookup tools tend to have less functionality than dig.
Source: MAN DIG
- Type A - Returns a 32-bit IPv4 address, most commonly used to map hostnames to an IP address of the host.
- Type AAAA - Returns a 128-bit IPv6 address, most commonly used to map hostnames to an IP address of the host.
- Type NS - Delegates a DNS zone to use the given authoritative name servers
- Type CNAME - lias of one name to another: the DNS lookup will continue by retrying the lookup with the new name. This helps when running multiple services (like an FTP and a webserver; each running on different ports) from a single IP address. Each service can then have its own entry in DNS (like ftp.example.com. and www.example.com.). Network administrators also use CNAMEs when running multiple HTTP servers on the same port, with different names, on the same physical host. This however requires host headers support for the two sites to both listen on the default port (port 80).
- Type SOA - Specifies authoritative information about a DNS zone, including the primary name server, the email of the domain administrator, the domain serial number, and several timers relating to refreshing the zone.
- Type PTR - Pointer to a canonical name. Unlike a CNAME, DNS processing does NOT proceed, just the name is returned. The most common use is for implementing reverse DNS lookups by putting a PTR record for a hostname in the in-addr.arpa. domain that corresponds to an IP address. For example (at the time of writing), www.icann.net has the IP address 126.96.36.199, but a PTR record maps 188.8.131.52.in-addr.arpa to its canonical name, referrals.icann.org.
- Type MX - Maps a domain name to a list of mail exchange servers for that domain
- Type TXT - Originally for arbitrary human-readable text in a DNS record. Since the early 1990s, however, this record more often carries machine-readable data, such as specified by RFC 1464, opportunistic encryption, Sender Policy Framework and DomainKeys.
- Type HINFO - an special HINFO record gives a description of the type of computer/OS a host uses
- Type ANY - Not a valid record type, but specifically a query type for DIG, NSLookup and tools alike. These queries request the tool to retrieve any information possible.