AWS Cloudformation CIDR block conflict - amazon-web-services

Question

I am currently trying to wrap my head around how to use AWS CloudFormation service. This might be a really simple question, but I think it is very hard to understand the platform so far.
I followed Amazon's tutorial on how to create a basic web server. Going off the final template from there, I want to modify it to enable a user-defined VPC IP range. For this, I tried to add a VPC CIDR Block property, as well as modify the PublicSubnet settings to get a /24 subnet from the block property, but when trying to create a stack I get the following error message:
Here's the template I am trying to use:
{
"AWSTemplateFormatVersion": "2010-09-09",
"Description": "AWS CloudFormation Sample Template VPC_Single_Instance_In_Subnet: Sample template showing how to create a VPC and add an EC2 instance with an Elastic IP address and a security group. **WARNING** This template creates an Amazon EC2 instance. You will be billed for the AWS resources used if you create a stack from this template.",
"Parameters": {
"InstanceType": {
"Description": "WebServer EC2 instance type",
"Type": "String",
"Default": "t2.micro",
"AllowedValues": [
"t1.micro",
"t2.micro",
"t2.small",
"t2.medium"
],
"ConstraintDescription": "must be a valid EC2 instance type."
},
"KeyName": {
"Description": "Name of an existing EC2 KeyPair to enable SSH access to the instance.",
"Type": "AWS::EC2::KeyPair::KeyName",
"ConstraintDescription": "must be the name of an existing EC2 KeyPair."
},
"SSHLocation": {
"Description": " The IP address range that can be used access the web server using SSH.",
"Type": "String",
"MinLength": "9",
"MaxLength": "18",
"Default": "0.0.0.0/0",
"AllowedPattern": "(\\d{1,3})\\.(\\d{1,3})\\.(\\d{1,3})\\.(\\d{1,3})/(\\d{1,2})",
"ConstraintDescription": "must be a valid IP CIDR range of the form x.x.x.x/x."
}
},
"Mappings": {
"AWSInstanceType2Arch": {
"t1.micro": {"Arch": "PV64"},
"t2.micro": {"Arch": "HVM64"},
"t2.small": {"Arch": "HVM64"},
"t2.medium": {"Arch": "HVM64"}
},
"AWSRegionArch2AMI": {
"us-east-1": {
"PV64": "ami-1ccae774",
"HVM64": "ami-1ecae776",
"HVMG2": "ami-8c6b40e4"
}
}
},
"Resources": {
"VPC": {
"Type": "AWS::EC2::VPC",
"Properties": {
"EnableDnsSupport": "true",
"EnableDnsHostnames": "true",
"CidrBlock": "10.0.0.0/16"
},
"Metadata": {
"AWS::CloudFormation::Designer": {"id": "96a791f0-938b-4ebe-9f3c-b3fe2a588aee"}
}
},
"VpcCidrBlock": {
"Type": "AWS::EC2::VPCCidrBlock",
"Properties": {
"VpcId": {"Ref": "VPC"},
"CidrBlock": "10.0.0.0/16"
}
},
"PublicSubnet": {
"Type": "AWS::EC2::Subnet",
"Properties": {
"CidrBlock": { "Fn::Select" : [ "0", { "Fn::Cidr" : ["10.0.0.0/24", 1, 8 ]}]},
"VpcId": {"Ref": "VPC"}
},
"Metadata": {
"AWS::CloudFormation::Designer": {"id": "3df467ad-673c-4c48-a41c-3ac1626961e3"}
}
},
"InternetGateway": {
"Type": "AWS::EC2::InternetGateway",
"Metadata": {
"AWS::CloudFormation::Designer": {"id": "a166c4f5-7cc4-429b-b9d8-2c8c43facc63"}
}
},
"VPCGatewayAttachment": {
"Type": "AWS::EC2::VPCGatewayAttachment",
"Properties": {
"VpcId": {"Ref": "VPC"},
"InternetGatewayId": {"Ref": "InternetGateway"}
},
"Metadata": {
"AWS::CloudFormation::Designer": {"id": "1790ebeb-2e41-4293-8cc1-aaba134fd1e0"}
}
},
"PublicRouteTable": {
"Type": "AWS::EC2::RouteTable",
"Properties": {
"VpcId": {"Ref": "VPC"}
},
"Metadata": {
"AWS::CloudFormation::Designer": {"id": "175bad80-0988-4588-a919-331be705b02d"}
}
},
"PublicRoute": {
"Type": "AWS::EC2::Route",
"DependsOn": "VPCGatewayAttachment",
"Properties": {
"RouteTableId": {"Ref": "PublicRouteTable"},
"DestinationCidrBlock": "0.0.0.0/0",
"GatewayId": {"Ref": "InternetGateway"}
},
"Metadata": {
"AWS::CloudFormation::Designer": {"id": "143bbaa1-66a2-42a5-885f-e6300817103c"}
}
},
"PublicSubnetRouteTableAssociation": {
"Type": "AWS::EC2::SubnetRouteTableAssociation",
"Properties": {
"SubnetId": {"Ref": "PublicSubnet"},
"RouteTableId": {"Ref": "PublicRouteTable"}
},
"Metadata": {
"AWS::CloudFormation::Designer": {"id": "528e2b71-46e6-4e09-815a-f70630755219"}
}
},
"WebServerSecurityGroup": {
"Type": "AWS::EC2::SecurityGroup",
"Properties": {
"VpcId": {"Ref": "VPC"},
"GroupDescription": "Allow access from HTTP and SSH traffic",
"SecurityGroupIngress": [
{
"IpProtocol": "tcp",
"FromPort": "80",
"ToPort": "80",
"CidrIp": "0.0.0.0/0"
},
{
"IpProtocol": "tcp",
"FromPort": "22",
"ToPort": "22",
"CidrIp": {"Ref": "SSHLocation"}
}
]
},
"Metadata": {
"AWS::CloudFormation::Designer": {"id": "2e76192b-a4f8-48a5-92b6-abbfa8b83263"}
}
},
"WebServerInstance": {
"Type": "AWS::EC2::Instance",
"Metadata": {
"AWS::CloudFormation::Init": {
"configSets": {
"All": ["ConfigureSampleApp"]
},
"ConfigureSampleApp": {
"packages": {
"yum": {
"httpd": []
}
},
"files": {
"/var/www/html/index.html": {
"content": {
"Fn::Join": [
"\n",
["<h1>Congratulations, you have successfully launched the AWS CloudFormation sample.</h1>"]
]
},
"mode": "000644",
"owner": "root",
"group": "root"
}
},
"services": {
"sysvinit": {
"httpd": {
"enabled": "true",
"ensureRunning": "true"
}
}
}
}
},
"AWS::CloudFormation::Designer": {"id": "0f900c9e-1272-4ec2-8a42-790b074baa39"}
},
"Properties": {
"InstanceType": {"Ref": "InstanceType"},
"ImageId": {
"Fn::FindInMap": [
"AWSRegionArch2AMI",
{"Ref": "AWS::Region"},
{
"Fn::FindInMap": [
"AWSInstanceType2Arch",
{"Ref": "InstanceType"},
"Arch"
]
}
]
},
"KeyName": {"Ref": "KeyName"},
"NetworkInterfaces": [
{
"GroupSet": [
{"Ref": "WebServerSecurityGroup"}
],
"AssociatePublicIpAddress": "true",
"DeviceIndex": "0",
"DeleteOnTermination": "true",
"SubnetId": {"Ref": "PublicSubnet"}
}
],
"UserData": {
"Fn::Base64": {
"Fn::Join": [
"",
[
"#!/bin/bash -xe\n",
"yum update -y aws-cfn-bootstrap\n",
"# Install the files and packages from the metadata\n",
"/opt/aws/bin/cfn-init -v ",
" --stack ",
{"Ref": "AWS::StackName"},
" --resource WebServerInstance ",
" --configsets All ",
" --region ",
{"Ref": "AWS::Region"},
"\n",
"# Signal the status from cfn-init\n",
"/opt/aws/bin/cfn-signal -e $? ",
" --stack ",
{"Ref": "AWS::StackName"},
" --resource WebServerInstance ",
" --region ",
{"Ref": "AWS::Region"},
"\n"
]
]
}
}
},
"CreationPolicy": {
"ResourceSignal": {"Timeout": "PT5M"}
}
}
},
"Outputs": {
"URL": {
"Value": {
"Fn::Join": [
"",
[
"http://",
{
"Fn::GetAtt": [
"WebServerInstance",
"PublicIp"
]
}
]
]
},
"Description": "Newly created application URL"
},
"SubnetCIDR": {
"Value": {"Ref": "PublicSubnet"},
"Description": "Subnet for the application"
}
},
"Metadata": {
"AWS::CloudFormation::Designer": {
"a166c4f5-7cc4-429b-b9d8-2c8c43facc63": {
"size": {
"width": 60,
"height": 60
},
"position": {
"x": -40,
"y": 210
},
"z": 1,
"embeds": []
},
"96a791f0-938b-4ebe-9f3c-b3fe2a588aee": {
"size": {
"width": 320,
"height": 250
},
"position": {
"x": 70,
"y": 190
},
"z": 1,
"embeds": [
"2e76192b-a4f8-48a5-92b6-abbfa8b83263",
"175bad80-0988-4588-a919-331be705b02d"
]
},
"2e76192b-a4f8-48a5-92b6-abbfa8b83263": {
"size": {
"width": 60,
"height": 60
},
"position": {
"x": 280,
"y": 370
},
"z": 2,
"parent": "96a791f0-938b-4ebe-9f3c-b3fe2a588aee",
"embeds": []
},
"175bad80-0988-4588-a919-331be705b02d": {
"size": {
"width": 120,
"height": 120
},
"position": {
"x": 90,
"y": 230
},
"z": 2,
"parent": "96a791f0-938b-4ebe-9f3c-b3fe2a588aee",
"embeds": ["143bbaa1-66a2-42a5-885f-e6300817103c"]
},
"1790ebeb-2e41-4293-8cc1-aaba134fd1e0": {
"source": {"id": "a166c4f5-7cc4-429b-b9d8-2c8c43facc63"},
"target": {"id": "96a791f0-938b-4ebe-9f3c-b3fe2a588aee"},
"z": 1
},
"143bbaa1-66a2-42a5-885f-e6300817103c": {
"size": {
"width": 60,
"height": 60
},
"position": {
"x": 120,
"y": 260
},
"z": 3,
"parent": "175bad80-0988-4588-a919-331be705b02d",
"embeds": [],
"references": ["a166c4f5-7cc4-429b-b9d8-2c8c43facc63"],
"dependson": ["1790ebeb-2e41-4293-8cc1-aaba134fd1e0"],
"isrelatedto": ["a166c4f5-7cc4-429b-b9d8-2c8c43facc63"]
},
"3df467ad-673c-4c48-a41c-3ac1626961e3": {
"size": {
"width": 120,
"height": 120
},
"position": {
"x": 250,
"y": 230
},
"z": 0,
"embeds": ["0f900c9e-1272-4ec2-8a42-790b074baa39"]
},
"0f900c9e-1272-4ec2-8a42-790b074baa39": {
"size": {
"width": 60,
"height": 60
},
"position": {
"x": 280,
"y": 260
},
"z": 3,
"parent": "3df467ad-673c-4c48-a41c-3ac1626961e3",
"embeds": [],
"isrelatedto": ["2e76192b-a4f8-48a5-92b6-abbfa8b83263"]
},
"13e0e0da-40c9-45d0-8460-7732ed20d764": {
"source": {"id": "96a791f0-938b-4ebe-9f3c-b3fe2a588aee"},
"target": {"id": "3df467ad-673c-4c48-a41c-3ac1626961e3"},
"z": 2
},
"528e2b71-46e6-4e09-815a-f70630755219": {
"source": {"id": "175bad80-0988-4588-a919-331be705b02d"},
"target": {"id": "3df467ad-673c-4c48-a41c-3ac1626961e3"},
"z": 2
}
}
}
}

Answer 1

You don't need AWS::EC2::VPCCidrBlock. Instead you add VPCCidr parameter to your template and use that:
{
"AWSTemplateFormatVersion": "2010-09-09",
"Description": "AWS CloudFormation Sample Template VPC_Single_Instance_In_Subnet: Sample template showing how to create a VPC and add an EC2 instance with an Elastic IP address and a security group. **WARNING** This template creates an Amazon EC2 instance. You will be billed for the AWS resources used if you create a stack from this template.",
"Parameters": {
"InstanceType": {
"Description": "WebServer EC2 instance type",
"Type": "String",
"Default": "t2.micro",
"AllowedValues": [
"t1.micro",
"t2.micro",
"t2.small",
"t2.medium"
],
"ConstraintDescription": "must be a valid EC2 instance type."
},
"KeyName": {
"Description": "Name of an existing EC2 KeyPair to enable SSH access to the instance.",
"Type": "AWS::EC2::KeyPair::KeyName",
"ConstraintDescription": "must be the name of an existing EC2 KeyPair."
},
"VPCCidr": {
"Type": "String",
"Default": "10.0.0.0/16"
},
"SSHLocation": {
"Description": " The IP address range that can be used access the web server using SSH.",
"Type": "String",
"MinLength": "9",
"MaxLength": "18",
"Default": "0.0.0.0/0",
"AllowedPattern": "(\\d{1,3})\\.(\\d{1,3})\\.(\\d{1,3})\\.(\\d{1,3})/(\\d{1,2})",
"ConstraintDescription": "must be a valid IP CIDR range of the form x.x.x.x/x."
}
},
"Mappings": {
"AWSInstanceType2Arch": {
"t1.micro": {"Arch": "PV64"},
"t2.micro": {"Arch": "HVM64"},
"t2.small": {"Arch": "HVM64"},
"t2.medium": {"Arch": "HVM64"}
},
"AWSRegionArch2AMI": {
"us-east-1": {
"PV64": "ami-1ccae774",
"HVM64": "ami-1ecae776",
"HVMG2": "ami-8c6b40e4"
}
}
},
"Resources": {
"VPC": {
"Type": "AWS::EC2::VPC",
"Properties": {
"EnableDnsSupport": "true",
"EnableDnsHostnames": "true",
"CidrBlock": {"Ref": "VPCCidr"}
},
"Metadata": {
"AWS::CloudFormation::Designer": {"id": "96a791f0-938b-4ebe-9f3c-b3fe2a588aee"}
}
},
"PublicSubnet": {
"Type": "AWS::EC2::Subnet",
"Properties": {
"CidrBlock": { "Fn::Select" : [ "0", { "Fn::Cidr" : [{"Ref": "VPCCidr"}, 1, 8 ]}]},
"VpcId": {"Ref": "VPC"}
},
"Metadata": {
"AWS::CloudFormation::Designer": {"id": "3df467ad-673c-4c48-a41c-3ac1626961e3"}
}
},
"InternetGateway": {
"Type": "AWS::EC2::InternetGateway",
"Metadata": {
"AWS::CloudFormation::Designer": {"id": "a166c4f5-7cc4-429b-b9d8-2c8c43facc63"}
}
},
"VPCGatewayAttachment": {
"Type": "AWS::EC2::VPCGatewayAttachment",
"Properties": {
"VpcId": {"Ref": "VPC"},
"InternetGatewayId": {"Ref": "InternetGateway"}
},
"Metadata": {
"AWS::CloudFormation::Designer": {"id": "1790ebeb-2e41-4293-8cc1-aaba134fd1e0"}
}
},
"PublicRouteTable": {
"Type": "AWS::EC2::RouteTable",
"Properties": {
"VpcId": {"Ref": "VPC"}
},
"Metadata": {
"AWS::CloudFormation::Designer": {"id": "175bad80-0988-4588-a919-331be705b02d"}
}
},
"PublicRoute": {
"Type": "AWS::EC2::Route",
"DependsOn": "VPCGatewayAttachment",
"Properties": {
"RouteTableId": {"Ref": "PublicRouteTable"},
"DestinationCidrBlock": "0.0.0.0/0",
"GatewayId": {"Ref": "InternetGateway"}
},
"Metadata": {
"AWS::CloudFormation::Designer": {"id": "143bbaa1-66a2-42a5-885f-e6300817103c"}
}
},
"PublicSubnetRouteTableAssociation": {
"Type": "AWS::EC2::SubnetRouteTableAssociation",
"Properties": {
"SubnetId": {"Ref": "PublicSubnet"},
"RouteTableId": {"Ref": "PublicRouteTable"}
},
"Metadata": {
"AWS::CloudFormation::Designer": {"id": "528e2b71-46e6-4e09-815a-f70630755219"}
}
},
"WebServerSecurityGroup": {
"Type": "AWS::EC2::SecurityGroup",
"Properties": {
"VpcId": {"Ref": "VPC"},
"GroupDescription": "Allow access from HTTP and SSH traffic",
"SecurityGroupIngress": [
{
"IpProtocol": "tcp",
"FromPort": "80",
"ToPort": "80",
"CidrIp": "0.0.0.0/0"
},
{
"IpProtocol": "tcp",
"FromPort": "22",
"ToPort": "22",
"CidrIp": {"Ref": "SSHLocation"}
}
]
},
"Metadata": {
"AWS::CloudFormation::Designer": {"id": "2e76192b-a4f8-48a5-92b6-abbfa8b83263"}
}
},
"WebServerInstance": {
"Type": "AWS::EC2::Instance",
"Metadata": {
"AWS::CloudFormation::Init": {
"configSets": {
"All": ["ConfigureSampleApp"]
},
"ConfigureSampleApp": {
"packages": {
"yum": {
"httpd": []
}
},
"files": {
"/var/www/html/index.html": {
"content": {
"Fn::Join": [
"\n",
["<h1>Congratulations, you have successfully launched the AWS CloudFormation sample.</h1>"]
]
},
"mode": "000644",
"owner": "root",
"group": "root"
}
},
"services": {
"sysvinit": {
"httpd": {
"enabled": "true",
"ensureRunning": "true"
}
}
}
}
},
"AWS::CloudFormation::Designer": {"id": "0f900c9e-1272-4ec2-8a42-790b074baa39"}
},
"Properties": {
"InstanceType": {"Ref": "InstanceType"},
"ImageId": {
"Fn::FindInMap": [
"AWSRegionArch2AMI",
{"Ref": "AWS::Region"},
{
"Fn::FindInMap": [
"AWSInstanceType2Arch",
{"Ref": "InstanceType"},
"Arch"
]
}
]
},
"KeyName": {"Ref": "KeyName"},
"NetworkInterfaces": [
{
"GroupSet": [
{"Ref": "WebServerSecurityGroup"}
],
"AssociatePublicIpAddress": "true",
"DeviceIndex": "0",
"DeleteOnTermination": "true",
"SubnetId": {"Ref": "PublicSubnet"}
}
],
"UserData": {
"Fn::Base64": {
"Fn::Join": [
"",
[
"#!/bin/bash -xe\n",
"yum update -y aws-cfn-bootstrap\n",
"# Install the files and packages from the metadata\n",
"/opt/aws/bin/cfn-init -v ",
" --stack ",
{"Ref": "AWS::StackName"},
" --resource WebServerInstance ",
" --configsets All ",
" --region ",
{"Ref": "AWS::Region"},
"\n",
"# Signal the status from cfn-init\n",
"/opt/aws/bin/cfn-signal -e $? ",
" --stack ",
{"Ref": "AWS::StackName"},
" --resource WebServerInstance ",
" --region ",
{"Ref": "AWS::Region"},
"\n"
]
]
}
}
},
"CreationPolicy": {
"ResourceSignal": {"Timeout": "PT5M"}
}
}
},
"Outputs": {
"URL": {
"Value": {
"Fn::Join": [
"",
[
"http://",
{
"Fn::GetAtt": [
"WebServerInstance",
"PublicIp"
]
}
]
]
},
"Description": "Newly created application URL"
},
"SubnetCIDR": {
"Value": {"Ref": "PublicSubnet"},
"Description": "Subnet for the application"
}
},
"Metadata": {
"AWS::CloudFormation::Designer": {
"a166c4f5-7cc4-429b-b9d8-2c8c43facc63": {
"size": {
"width": 60,
"height": 60
},
"position": {
"x": -40,
"y": 210
},
"z": 1,
"embeds": []
},
"96a791f0-938b-4ebe-9f3c-b3fe2a588aee": {
"size": {
"width": 320,
"height": 250
},
"position": {
"x": 70,
"y": 190
},
"z": 1,
"embeds": [
"2e76192b-a4f8-48a5-92b6-abbfa8b83263",
"175bad80-0988-4588-a919-331be705b02d"
]
},
"2e76192b-a4f8-48a5-92b6-abbfa8b83263": {
"size": {
"width": 60,
"height": 60
},
"position": {
"x": 280,
"y": 370
},
"z": 2,
"parent": "96a791f0-938b-4ebe-9f3c-b3fe2a588aee",
"embeds": []
},
"175bad80-0988-4588-a919-331be705b02d": {
"size": {
"width": 120,
"height": 120
},
"position": {
"x": 90,
"y": 230
},
"z": 2,
"parent": "96a791f0-938b-4ebe-9f3c-b3fe2a588aee",
"embeds": ["143bbaa1-66a2-42a5-885f-e6300817103c"]
},
"1790ebeb-2e41-4293-8cc1-aaba134fd1e0": {
"source": {"id": "a166c4f5-7cc4-429b-b9d8-2c8c43facc63"},
"target": {"id": "96a791f0-938b-4ebe-9f3c-b3fe2a588aee"},
"z": 1
},
"143bbaa1-66a2-42a5-885f-e6300817103c": {
"size": {
"width": 60,
"height": 60
},
"position": {
"x": 120,
"y": 260
},
"z": 3,
"parent": "175bad80-0988-4588-a919-331be705b02d",
"embeds": [],
"references": ["a166c4f5-7cc4-429b-b9d8-2c8c43facc63"],
"dependson": ["1790ebeb-2e41-4293-8cc1-aaba134fd1e0"],
"isrelatedto": ["a166c4f5-7cc4-429b-b9d8-2c8c43facc63"]
},
"3df467ad-673c-4c48-a41c-3ac1626961e3": {
"size": {
"width": 120,
"height": 120
},
"position": {
"x": 250,
"y": 230
},
"z": 0,
"embeds": ["0f900c9e-1272-4ec2-8a42-790b074baa39"]
},
"0f900c9e-1272-4ec2-8a42-790b074baa39": {
"size": {
"width": 60,
"height": 60
},
"position": {
"x": 280,
"y": 260
},
"z": 3,
"parent": "3df467ad-673c-4c48-a41c-3ac1626961e3",
"embeds": [],
"isrelatedto": ["2e76192b-a4f8-48a5-92b6-abbfa8b83263"]
},
"13e0e0da-40c9-45d0-8460-7732ed20d764": {
"source": {"id": "96a791f0-938b-4ebe-9f3c-b3fe2a588aee"},
"target": {"id": "3df467ad-673c-4c48-a41c-3ac1626961e3"},
"z": 2
},
"528e2b71-46e6-4e09-815a-f70630755219": {
"source": {"id": "175bad80-0988-4588-a919-331be705b02d"},
"target": {"id": "3df467ad-673c-4c48-a41c-3ac1626961e3"},
"z": 2
}
}
}
}