Can a subnet be associated with multiple Access Control Lists (ACLs)?

A subnet in AWS can be associated with only one Network Access Control List (ACL) at any given time. This is a fundamental aspect of how network security is managed within the Amazon Virtual Private Cloud (VPC) architecture. The design allows for a single point of control for inbound and outbound traffic rules at the subnet level. By enforcing one ACL per subnet, AWS simplifies the management of rules while ensuring consistency in traffic control.

When a subnet is associated with a specific ACL, the rules defined within that ACL apply to all the resources within the subnet. If you need to change the behavior of network traffic for that subnet, you would modify the existing ACL or attach a different one, but still, only one ACL can be attached at a time.

This approach provides clarity and reduces complexity, as having multiple ACLs associated with a single subnet could lead to confusion about which set of rules is in effect. Therefore, the assertion that a subnet can only have one ACL associated with it at any given time is true and reflects the design principles of AWS's networking capabilities.