DNS - Basics
Domain Name System (DNS)
The Domain Name System (DNS) is a distributed database responsible for translating domain names into IP addresses. It’s composed of a hierarchical structure that is divided into several zones, starting with the top-level root zone.
Each domain can use different types of DNS records. Some of the most common types of DNS records include:
- NS: Nameserver records contain the name of the authoritative servers hosting the DNS records for a domain.
- A: Also known as a host record, the “a record” contains the IPv4 address of a hostname
- AAAA: Also known as a quad A host record, the “aaaa record” contains the IPv6 address of a hostname
- MX: Mail Exchange records contain the names of the servers responsible for handling email for the domain. A domain can contain multiple MX records.
- PTR: Pointer Records are used in reverse lookup zones and can find the records associated with an IP address.
- CNAME: Canonical Name Records are used to create aliases for other host records.
- TXT: Text records can contain any arbitrary data and be used for various purposes, such as domain ownership verification.
We can use the host command to find IP addresses (default search for A records):
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google.com has address 172.217.4.206
google.com has IPv6 address 2607:f8b0:4009:81c::200e
google.com mail is handled by 10 smtp.google.com.
The -t option can be used to search for other records:
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google.com descriptive text "apple-domain-verification=30afIBcvSuDV2PLX"
google.com descriptive text "facebook-domain-verification=22rm551cu4k0ab0bxsw536tlds4h95"
google.com descriptive text "docusign=1b0a6754-49b1-4db5-8540-d2c12664b289"
google.com descriptive text "globalsign-smime-dv=CDYX+XFHUw2wml6/Gb8+59BsH31KzUr6c1l2BPvqKX8="
google.com descriptive text "onetrust-domain-verification=de01ed21f2fa4d8781cbc3ffb89cf4ef"
google.com descriptive text "MS=E4A68B9AB2BB9670BCE15412F62916164C0B20BB"
google.com descriptive text "v=spf1 include:_spf.google.com ~all"
google.com descriptive text "webexdomainverification.8YX6G=6e6922db-e3e6-4a36-904e-a805c28087fa"
google.com descriptive text "google-site-verification=wD8N7i1JTNTkezJ49swvWW48f8_9xveREV4oB-0Hf5o"
google.com descriptive text "atlassian-domain-verification=5YjTmWmjI92ewqkx2oXmBaD60Td9zWon9r6eakvHX6B77zzkFQto8PQ9QsKnbf4I"
google.com descriptive text "google-site-verification=TV9-DBe4R80X4v0M4U_bd_J9cpOJM0nikft0jAgjmsQ"
google.com descriptive text "docusign=05958488-4752-4ef2-95eb-aa7ba8a3bd0e"