This read-create object of type AclDefaultAction defines the fallback action applied to egress traffic on an interface when none of the configured rules in an egress ACL match a packet. It matters to an admin because it determines whether unmatched outbound traffic is permitted or dropped by default once an egress ACL is attached to an interface. For example, an admin might set this to deny so that any outbound packet not explicitly permitted by the egress ACL's rules is dropped as a last resort.