I've wanted to add couple of internal firewalls (opnsense/pfsense) and have them report to my zabbix server on a VPS.
I didn't want to open any ports for passive checks, so I edited the default FreeBSD by Zabbix Agent template, and changed every Item to zabbix agent active.

Removed Agent availability as it seems to only work with passive checks.

It seems to get data for both *sense boxes.

I've attached the template, I don't have any experience with Zabbix (started poking 2 days ago). So I'd be more comfortable someone verify this template and ultimately make a PR to add this.

Just keep in mind that I blindly:

• Changed every item from zabbix agent to zabbix agent active
• Changed every discovery rule and Item prototypes from zabbix agent to zabbix agent active
• Removed Agent Availability