Create Network Acl Entry Response from the service

Each network ACL has a set of numbered ingress rules and a separate set of numbered egress rules. When determining whether a packet should be allowed in or out of a subnet associated with the ACL, Amazon VPC processes the entries in the ACL according to the rule numbers, in ascending order. We recommend that you leave room between the rules (e.g., 100, 110, 120, etc.), and not number them sequentially (101, 102, 103, etc.). This allows you to easily add a new rule between existing ones without having to renumber the rules. After you add an entry, you can't modify it; you must either replace it, or create a new entry and delete the old one.