https://datatracker.ietf.org/doc/rfc3342/
RFC 3342 - The Application Exchange (APEX) Option Party Pack, Part Deux!
APEX, at its core, provides a best-effort application-layer datagram service. Options are used to alter the semantics of the core service. This memo defines...
the applicationapex optionparty packrfcexchange
https://success.trendmicro.com/en-US/solution/KA-0009175
FQDN does not appear as an option when installing Apex Central
does notfqdnappear