PTR record is used for which type of DNS lookup?

PTR record is used for which type of DNS lookup?

• A. CNAME lookup
• B. Reverse DNS lookup
• C. Forward DNS lookup
• D. MX lookup

Answer: (B)

PTR records are used for reverse DNS lookups. A PTR (pointer) record provides the mapping from an IP address back to a host name, so you can start with an IP and discover the associated domain name. This reverse process uses special namespaces: in-addr.arpa for IPv4 and ip6.arpa for IPv6. By contrast, forward lookups resolve a domain name to an IP address using A (IPv4) or AAAA (IPv6) records. Other common records serve different purposes—CNAME for aliases, MX for mail servers—so they aren’t used for mapping IPs back to names.

PTR records are used for reverse DNS lookups. A PTR (pointer) record provides the mapping from an IP address back to a host name, so you can start with an IP and discover the associated domain name. This reverse process uses special namespaces: in-addr.arpa for IPv4 and ip6.arpa for IPv6. By contrast, forward lookups resolve a domain name to an IP address using A (IPv4) or AAAA (IPv6) records. Other common records serve different purposes—CNAME for aliases, MX for mail servers—so they aren’t used for mapping IPs back to names.