related to outgoing and incomming interface of cisco router

nixdaemon000

How does the router knows that which interface is inbound and which interface is outbound?
This is related to access-list.

CaptainCharisma

Each interface is inbound and outbound, you just have to think logically how the data is traveling. If the data starts outside the router, the interface it goes in on will have to have an inbound ACL applied. After the data has gone in through an interface it has to go out another interface, so the data is inside the router now and it will be exiting the router through an interface so the ACL applied to the interface that the data exits the router from would be an outbound ACL.

You may only need to apply an ACL in one direction and the instances for applying an inbound or outbound varies.