When when on Cisco to apply an ACL on the ingress and when on the egress of an interface?

Question

Cisco

Hello!
I just can’t catch a clear difference between
ip access-group in
and
ip access-group out
Please help me understand the principle by which it would be possible to immediately determine in which cases ACL should be hung on the output (out), and when on the input (in) of the interface?

Answer 1

on in any incoming connections (what came to your network), on out - outgoing (what will leave your network).

Answer 2

To determine where to hang the access list, there is a rule - you should always look relative to the device in for traffic that enters the device, out for outgoing from the device.