Provides a resource to manage a VPC's default network ACL. This resource can manage the default network ACL of the default or a non-default VPC.
Every VPC has a default network ACL that can be managed but not destroyed. When Terraform first adopts the Default Network ACL, it immediately removes all rules in the ACL. It then proceeds to create any rules specified in the configuration. This step is required so that only the rules specified in the configuration are created.
This resource treats its inline rules as absolute; only the rules defined inline are created, and any additions/removals external to this resource will result in diffs being shown. For these reasons, this resource is incompatible with the aws_network_acl_rule
resource.
For more information about Network ACLs, see the AWS Documentation on Network ACLs.
The following config gives the Default Network ACL the same rules that AWS includes but pulls the resource under management by Terraform. This means that any ACL rules added or changed will be detected as drift.
resource "aws_vpc" "mainvpc" {
cidr_block = "10.1.0.0/16"
}
resource "aws_default_network_acl" "default" {
default_network_acl_id = aws_vpc.mainvpc.default_network_acl_id
ingress {
protocol = -1
rule_no = 100
action = "allow"
cidr_block = "0.0.0.0/0"
from_port = 0
to_port = 0
}
egress {
protocol = -1
rule_no = 100
action = "allow"
cidr_block = "0.0.0.0/0"
from_port = 0
to_port = 0
}
}
The following denies all Egress traffic by omitting any egress
rules, while including the default ingress
rule to allow all traffic.
resource "aws_vpc" "mainvpc" {
cidr_block = "10.1.0.0/16"
}
resource "aws_default_network_acl" "default" {
default_network_acl_id = aws_vpc.mainvpc.default_network_acl_id
ingress {
protocol = -1
rule_no = 100
action = "allow"
cidr_block = aws_default_vpc.mainvpc.cidr_block
from_port = 0
to_port = 0
}
}
This config denies all traffic in the Default ACL. This can be useful if you want to lock down the VPC to force all resources to assign a non-default ACL.
resource "aws_vpc" "mainvpc" {
cidr_block = "10.1.0.0/16"
}
resource "aws_default_network_acl" "default" {
default_network_acl_id = aws_vpc.mainvpc.default_network_acl_id
# no rules defined, deny all traffic in this ACL
}
Within a VPC, all Subnets must be associated with a Network ACL. In order to "delete" the association between a Subnet and a non-default Network ACL, the association is destroyed by replacing it with an association between the Subnet and the Default ACL instead.
When managing the Default Network ACL, you cannot "remove" Subnets. Instead, they must be reassigned to another Network ACL, or the Subnet itself must be destroyed. Because of these requirements, removing the subnet_ids
attribute from the configuration of a aws_default_network_acl
resource may result in a reoccurring plan, until the Subnets are reassigned to another Network ACL or are destroyed.
Because Subnets are by default associated with the Default Network ACL, any non-explicit association will show up as a plan to remove the Subnet. For example: if you have a custom aws_network_acl
with two subnets attached, and you remove the aws_network_acl
resource, after successfully destroying this resource future plans will show a diff on the managed aws_default_network_acl
, as those two Subnets have been orphaned by the now destroyed network acl and thus adopted by the Default Network ACL. In order to avoid a reoccurring plan, they will need to be reassigned, destroyed, or added to the subnet_ids
attribute of the aws_default_network_acl
entry.
As an alternative to the above, you can also specify the following lifecycle configuration in your aws_default_network_acl
resource:
resource "aws_default_network_acl" "default" {
# ... other configuration ...
lifecycle {
ignore_changes = [subnet_ids]
}
}
aws_default_network_acl
From Your ConfigurationEach AWS VPC comes with a Default Network ACL that cannot be deleted. The aws_default_network_acl
allows you to manage this Network ACL, but Terraform cannot destroy it. Removing this resource from your configuration will remove it from your statefile and management, but will not destroy the Network ACL. All Subnets associations and ingress or egress rules will be left as they are at the time of removal. You can resume managing them via the AWS Console.
The following arguments are required:
default_network_acl_id
- (Required) Network ACL ID to manage. This attribute is exported from aws_vpc
, or manually found via the AWS Console.The following arguments are optional:
egress
- (Optional) Configuration block for an egress rule. Detailed below.ingress
- (Optional) Configuration block for an ingress rule. Detailed below.subnet_ids
- (Optional) List of Subnet IDs to apply the ACL to. See the notes above on Managing Subnets in the Default Network ACLtags
- (Optional) Map of tags to assign to the resource. If configured with a provider default_tags
configuration block present, tags with matching keys will overwrite those defined at the provider-level.Both the egress
and ingress
configuration blocks have the same arguments.
The following arguments are required:
action
- (Required) The action to take.from_port
- (Required) The from port to match.protocol
- (Required) The protocol to match. If using the -1 'all' protocol, you must specify a from and to port of 0.rule_no
- (Required) The rule number. Used for ordering.to_port
- (Required) The to port to match.The following arguments are optional:
cidr_block
- (Optional) The CIDR block to match. This must be a valid network mask.icmp_code
- (Optional) The ICMP type code to be used. Default 0.icmp_type
- (Optional) The ICMP type to be used. Default 0.ipv6_cidr_block
- (Optional) The IPv6 CIDR block.This resource exports the following attributes in addition to the arguments above:
arn
- ARN of the Default Network ACLid
- ID of the Default Network ACLowner_id
- ID of the AWS account that owns the Default Network ACLtags_all
- A map of tags assigned to the resource, including those inherited from the provider default_tags
configuration block.vpc_id
- ID of the associated VPCIn Terraform v1.5.0 and later, use an import
block to import Default Network ACLs using the id
. For example:
import {
to = aws_default_network_acl.sample
id = "acl-7aaabd18"
}
Using terraform import
, import Default Network ACLs using the id
. For example:
% terraform import aws_default_network_acl.sample acl-7aaabd18