NATD: net.inet.ip.fw.default_to_accept="1" vs firewall_type="OPEN"

[Chris Stankevitz]

Hello,

Handbook section 31.9 describes the setup of NAT.

Section 31.9.3 suggests net.inet.ip.fw.default_to_accept="1" "during
the first attempts to setup a firewall and NAT gateway".

Section 31.9.5 suggests I "specify a predefined firewall ruleset that
allows anything in" with firewall_type="OPEN"

Question: What is the difference between these two configurations (or
where can I go to learn the difference between the two)?

Thank you,

Chris