In order for the IP address to be resolved from the fully qualified domain name (FQDN), we need a reverse lookup file on the DNS server. This is named db.x.y.z, for example db.0.21.156.188. In this file the computer name (FQDN) is assigned to the last octet of an IP address, which corresponds to the respective host, by means of a PTR record. The PTR records are responsible for the reverse translation of IP addresses into names.
;; db.0.21.156.188
$TTL 2D
@ IN SOA ns1.mycompany.com. hosmaster@mycompany.com. (
2018012002 ; Serial
3H ; refresh after 3 hours
1H ; retry after 1 hour
1W ; expire after 1 week
1D) ; minimum TTL of 1 day
@ IN NS ns1.mycompany.com.
10 IN PTR mail.mycompany.com.
20 IN PTR www.mycompany.com.
150 IN PTR app.mycompany.com.
Importantly, the translated names are the FQDNs that end with a dot.
The performance of alias entries, MX records, etc. does not happen again here.