Let's quickly go through some important concepts related to network ACLs:
- When we create a VPC, a default NACL is created by AWS. The value of the Default column will be Yes for the default NACL within the NACL list in our VPC.
- Default NACL allows all inbound and outbound traffic. However, when we create a new custom NACL, all the inbound and outbound traffic is denied by default.
- Every subnet needs to be associated with one NACL at a time. By default, a subnet is associated with the default NACL.
- One subnet can only be associated with one NACL at a time. When we associate it with a new NACL, the current association will be removed.
- A single NACL can be associated with multiple subnets.
- NACLs contain a numbered set of rules. ...