iptables

iptables / nftables

In the Army, we had “Checkpoint Procedures.” iptables and its successor nftables are the foundational checkpoint procedures for Linux.

Description

• iptables: The traditional Linux firewall interface that manages rules for network packets.
• nftables: The modern replacement for iptables that offers a more efficient and flexible syntax.

Knowledge Check

• Have you flushed your existing rules before starting a new configuration?
• Are your rules being persisted across reboots?

Common Pitfalls

• Order of Operations: Rules are processed in order. If you have a “Drop All” rule at the top, nothing will get through.
• Locking Yourself Out: ALWAYS have a way back in (e.g., local console) before you apply new firewall rules remotely.