Книга: Iptables Tutorial 1.2.2

Setting up default policies

Setting up default policies

Quite early on in the process of creating our rule-set, we set up the default policies. We set up the default policies on the different chains with a fairly simple command, as described below.

iptables [-P {chain} {policy}]

The default policy is used every time the packets do not match a rule in the chain. For example, let's say we get a packet that matches no single rule in our whole rule-set. If this happens, we must decide what should happen to the packet in question, and this is where the default policy comes into the picture. The default policy is used on all packets that does not match with any other rule in our rule-set.

Caution! Do be cautious with what default policy you set on chains in other tables since they are simply not made for filtering, and it may lead to very strange behaviors.

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