The plot thickens: we do our printing thru a third party program called
ESPUL.

ESPUL does have a config file, but it does not have IP addresses for every
printer as far as I can tell. (Many networked printers do have IP addresses
in the ESPUL config file, but some do not - I do not know why the
difference).  I would like a source of IP addresses for every printer that,
in fact, actually has an IP address.