フリー問題

問題文

A rule at the address level drops traffic from a subnet, yet traffic from that subnet is still being carried through the system. What explains it?

選択肢

1. The rules are read after the ones that the system supplies for itself, since a rule that the system supplies allows the traffic of every service that it runs.
2. The rules are held in a pending state until the next set is put into force, since a change on one interface waits for the other one.
3. The rules reach only the traffic that is fresh and inbound, since the reply to a connection raised from the inside is taken in whatever the rules say.
4. The rules leave the traffic of the interface that carries the second network alone, since a rule of this kind is drawn up for one interface and not for the pair.