Section 9.1 of the Handbook gives nice examples of /etc/printcap files that can be used for printing. The one for a networked printer says to include the DNS FQDN of the printer.
This isn't always either possible or desirable. Printers should generally not be connected to the public routed Internet except in some very special cases because of the potential for security issues. Furthermore, in those cases where the IP address of a networked printer is one that is not publicly routable, that address should not appear in DNS records, according to published IETF guidance:
Fortunately, it appears that at the point in the example /etc/printcap file where the user it told to substitute in the DNS name of the networked printer, if the user instead substitutes in a traditional dotted quad representation of the networked printer's IPv4 address, this seems to work just as well as if there had been a DNS fully qualified domain name for the networked printer substituted at that point in the /etc/printcap file instead.
Readers of the Handbook should be advised of this alternative possible way of designating a networked printer.
Readers of the Handbook should perhaps also be advised that a networked printer that can operate either in DHCP mode or in static address mode may possibly be easier to deal with (for printing from FreeBSD) if the printer is assigned a static IP address.