(Cisco) ACL direction (in/out)?

An access control list (ACL) is an important security tool used to control the flow of traffic in and out of a device or network. It is used to define which traffic is allowed or denied based on certain criteria, such as source and destination address or port numbers.

ACLs are commonly used in routers and firewalls to prevent malicious traffic from entering the network. They can also be used to protect internal network resources from external threats.

In Cisco devices, ACLs are configured in either of two directions: outbound or inbound. Outbound ACLs are placed on the interface of the device that is connected to the network, and they control traffic that is leaving the device. This type of ACL is typically used to protect the device from unwanted traffic.

Inbound ACLs are placed on the interface of the device that is connected to the external network, and they control traffic that is entering the device. This type of ACL is typically used to protect the internal network from external threats.

When configuring ACLs, it is important to consider the direction of the traffic. Outbound ACLs should be configured on the interface that is connected to the network, and inbound ACLs should be configured on the interface that is connected to the external network.

It is also important to remember that the rules in an ACL should be configured from most specific to least specific, meaning that the most restrictive rules should be placed at the top of the list. This will ensure that only traffic that matches the most specific criteria is allowed.

To sum up, an ACL is a powerful security tool used to control traffic flow in and out of a device or network. Cisco devices support two types of ACLs, outbound and inbound, and it is important to consider the direction of the traffic when configuring them. Outbound ACLs should be placed on the interface connected to the network, while inbound ACLs should be placed on the interface connected to the external network. Finally, the rules in an ACL should be configured from most specific to least specific, to ensure that only traffic that matches the most specific criteria is allowed.