There used to be these sysctls in older versions of FreeBSD, viz:


now on FreeBSD 12 sysctl reports that these don't exist.

How can I tune the lifetime for TCP/UDP for in kernel NAT?

  • They are still there. Did you forget to load it? ipfw_load="YES" Commented Aug 20, 2021 at 23:43

1 Answer 1


I found the answer. Basically I was looking at the wrong documentation :-)

I'm actually using pf, and equivalent tunables are documented in the pf.conf man pages, under the section for the set command, specifically set timeout in this case.

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