install | setup | routing states
tested on slack150 and debian12
the packages at hand
    apt install conntrack conntrackd
ls -lF /etc/conntrackd/primary-backup.sh # no exist
    ln -s /usr/share/doc/conntrackd/examples/sync/primary-backup.sh /etc/conntrackd/primary-backup.sh
you need to enable Netfilter connection tracker
apt install nftables
and a few handy tools won’t hurt
apt install netstat-nat tcpdump
    slackpkg install nftables
    slackpkg install libmnl
    slackpkg install libnfnetlink
    slackpkg install libnetfilter_conntrack
    slackpkg install conntrack-tools
#+tcpdump
ln -s /usr/doc/conntrack-tools-1.4.6/sync/primary-backup.sh /etc/conntrackd/primary-backup.sh
    sbopkg -i netstat-nat