Linux network debugging: iptables rules, connection tracking table, packet tracking

Use the LOG module to print messages at any position

iptables -t raw -A OUTPUT -m limit --limit 5000/minute -j LOG --log-level 7 --log-prefix "raw out: "
iptables -t mangle -A OUTPUT -m limit --limit 5000/minute -j LOG --log-level 7 --log-prefix "mangle out: "
iptables -t nat -A OUTPUT -m limit --limit 5000/minute -j LOG --log-level 7 --log-prefix "nat out: "
iptables -t filter -A OUTPUT -m limit --limit 5000/minute -j LOG --log-level 7 --log-prefix "filter out: "
iptables -t mangle -A POSTROUTING -m limit --limit 5000/minute -j LOG --log-level 7 --log-prefix "mangle post: "
iptables -t nat -A POSTROUTING -m limit --limit 5000/minute -j LOG --log-level 7 --log-prefix "nat post: "

Reference

• iptables rules, connection tracking table, packet tracking