USING IPFW2 IN FreeBSD-STABLE
ipfw2 is standard in FreeBSD CURRENT, whereas FreeBSD STABLE still uses
ipfw1 unless the kernel is compiled with options IPFW2, and /sbin/ipfw
and /usr/lib/libalias are recompiled with -DIPFW2 and reinstalled (the
same effect can be achieved by adding IPFW2=TRUE to /etc/make.conf before
a buildworld).
4.8-RELEASE の ipfw の man (スコア:1)
ipfw2 is standard in FreeBSD CURRENT, whereas FreeBSD STABLE still uses
ipfw1 unless the kernel is compiled with options IPFW2, and /sbin/ipfw
and /usr/lib/libalias are recompiled with -DIPFW2 and reinstalled (the
same effect can be achieved by adding IPFW2=TRUE to /etc/make.conf before
a buildworld).
こういう記述になっているようです。そういう意味で以前から使えたと思います。