About iptables. I saw contradictory explanations.

This site and most article say PREROUTING chain is checked before INPUT chain. But another tutorial(page 4-6) says INPUT is before PREROUTING. Whom to trust?


The official netfilter doc states that the PREROUTING is checked before the INPUT chain. The following diagram is taken directly from the doc:

    Conntrack    |       Mangle   ^    Mangle
    Mangle       |       Filter   |    NAT (Src)
    NAT (Dst)    |                |    Conntrack
    (QDisc)      |             [ROUTE]
                 v                |
                 IN Filter       OUT Conntrack
                 |  Conntrack     ^  Mangle
                 |  Mangle        |  NAT (Dst)
                 v                |  Filter

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