Which of the following keywords are built-in chairs for the iptables nat table? (Choose THREE correct answers.)

Question

Options

• AOUTPUT
• BMASQUERADE
• CPROCESSING
• DPOSTROUTING
• EPREROUTING

• A
  86% (54)
• B
  5% (3)
• C
  10% (6)

Explanation

The iptables nat table contains exactly three built-in chains: PREROUTING (E), which intercepts packets as they arrive before routing decisions are made; OUTPUT (A), which handles locally-generated packets before they are routed; and POSTROUTING (D), which processes packets after routing, just before they leave the system - making these the correct answers.

MASQUERADE (B) is not a chain at all - it is a target (an action/jump destination) used inside rules, typically in POSTROUTING, to dynamically rewrite the source IP for outgoing connections. PROCESSING (C) is simply invented; no such chain or keyword exists in iptables.

Memory tip: Think of packet flow order - PRErouting → route decision → POSTrouting, and locally-generated traffic takes an OUTPUT shortcut. If it's a verb describing what happens to a packet, it's likely a chain; if it describes an action applied to a packet (like MASQUERADE, DNAT, SNAT), it's a target.

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