Which of the following DNS record types is used to allow users and applications to make reverse DNS queries?

Marit C.Apr 18, 2026

PTR is the answer, option C. Reverse DNS maps an IP address back to a hostname, and that lookup lives in the in-addr.arpa zone (or ip6.arpa for IPv6), where PTR records are the mechanism that makes the response possible. When a resolver issues a reverse query, it constructs the reversed-octet dotted name, for example 1.168.192.in-addr.arpa, and the authoritative name server returns a PTR record pointing to the fully qualified domain name. CNAME is an alias for forward lookups, IN is simply the Internet class field you see in zone file syntax, and REV and RIN are not real DNS record types at all, just distractors.

Dervla O.Apr 24, 2026

PTR is the record type that maps an IP address back to a hostname, which is the whole point of a reverse lookup. When you run a tool like nslookup or dig against an IP, the resolver is actually querying a PTR record stored under the special in-addr.arpa domain. The other options here are distractors worth understanding: CNAME creates an alias between hostnames, IN is a DNS class designator you will see in zone file syntax, and REV plus RIN are simply not real record types. One thing worth drilling before exam day is how a reverse lookup zone is actually structured in a zone file, because that context explains why PTR exists as its own record type rather than A records handling both directions. Have you worked through what the in-addr.arpa notation looks like for a given IP address, and do you understand why the octets are written in reverse order?

Carlos M.May 2, 2026

PTR record maps an IP address back to a hostname, that's your reverse DNS lookup.

Mateus R.May 7, 2026

The "IN" option is a sneaky trap because IN is actually the class designation you see in a zone file entry (it stands for Internet, the address family), so it sounds vaguely DNS-official, but a class label is not a record type. PTR is your answer, and the way to remember it is like a return address on an envelope: you know the street address (the IP) and you want to find the name on the mailbox, so you do a pointer lookup in the in-addr.arpa zone.

Ola B.May 11, 2026

I have been spinning up BIND labs all week and I keep coming back to A, CNAME, because canonical name records are the glue that maps one name to another, which is exactly what a reverse lookup is doing, mapping an address back to a canonical hostname. When you trace what happens in a resolver when a reverse query comes in, you see that the chain has to terminate at a name, and CNAME is the record type built for that name aliasing relationship. I set up a test zone in my home lab, dropped in a CNAME pointing my IP notation back to my hostname, and the reverse resolution worked clean. Go build it yourself in a local BIND or dnsmasq instance before the exam and you will see what I mean, the lab does not lie.