Where is it best to deploy access lists for strong infrastructure device protection?

Deploying access lists in the ingress direction on all IP-configured interfaces is the optimal approach for strong infrastructure device protection for several reasons.

First, placing access lists on ingress interfaces allows for filtering incoming traffic before it reaches the device's resources, therefore providing a first line of defense against unwanted or malicious traffic. This optimizes security by ensuring that potentially harmful packets do not create additional load on the device or risk exposing vulnerabilities.

Moreover, ingress filtering can help in identifying and blocking spoofed addresses from untrusted sources, reducing the chance of attacks that leverage unauthorized access to the device. By handling these concerns at the point of entry, the infrastructure is protected more effectively because it minimizes the attack surface right at the boundary of the network.

In contrast, other approaches, such as deploying access lists on egress to filter outgoing traffic or on specific interfaces, can lead to vulnerabilities. For instance, outbound filtering may not adequately guard against attack vectors that operate through incoming traffic, which can lead to an increased risk if the access lists are not comprehensive.

Thus, deploying access lists in the ingress direction on all IP-configured interfaces ensures that any harmful traffic is dealt with promptly, maintaining the overall security posture of the infrastructure.