DNS: Resource Records

Resourse Records (RRs) used to identify objects within DNS hierarchy / basic lookups within specified domain. Key RRs types are following (7):\n\nSOA (Start of Authority) Records – indicate which server is authoritative for that particular zone. Indicate authoritative server for zone which also in charge for processing zone updates. Also contains some critical zone information like TTL interval, contact responsible for DNS etc. Created automatically when DNS is installed for AD DS.\n\nHost (A) Records – most widely used RR type, simply contains name of the host & its IP address. Used to identify IP address of objects.\n\nName Server (NS) Records – identify which computers are name servers for a particular zone (i.e. DNS servers). There can be only one SOA record for a zone but multiple NS records indicating computers against which you may run DNS queries. NS RRs don’t contain IP but simply point to a server A record.\n\nService (SRV) Records – indicate which resources perform particular service. E.g. DCs referenced by SRV records which define specific services like GC, LDAP, Kerberos. SRV records did not exist in original DNS standard, so don’t supported by some old DNS implementations (like UNIX BIND 4.1.x or NT 4.0 DNS). BIND 8.1.2+ supports SRV records.\n\nMail Exchanger (MX) records – indicates resources available for SMTP reception, so that mail send to particular domain forwarded to server/servers indicated by the MX record.\n\nPointer (PTR) RRs – for reverse queries (i.e. lookup for names by IP), stored in reverse lookup zones.\n\nCanonical name (CNAME) Records – server alias, to refer server by multiple names. E.g. friendly name for mail server in addition to its complex name following some naming convention.\n\nLess commonly used RRs:\n\nAAAA – IPv6 A record\n\nISDN – maps DNS name to ISDN phone number\n\nKEY – stores public key used for encryption in particular domain\n\nRP – specifies responsible person for domain\n\nWKS – designates a particular Well-Known Service\n\nMB – indicates host which contains a specific mailbox