cloudformation failed to create subnets - json

Question

I was trying to run a code and i had this error but cant identify the problem. i got the error message The CIDR '10.0.1.0/24' conflicts with another subnet (Service: AmazonEC2; Status Code: 400; Error Code: InvalidSubnet.Conflict; Request ID: e0de23a8-d921-475f-aadd-84dac3109664; Proxy: null)
{
"AWSTemplateFormatVersion": "2010-09-09",
"Description": "This is a network with one Vpc, 4 Subnet; 2 private, 2 public",
"Metadata": {},
"Parameters": {
"MyVpcCidr": {
"Description": "This is the cidr for appVpc",
"Type": "String",
"Default": "10.0.0.0/16"
},
"AZ1": {
"Description": "AZ 1 for my network",
"Type": "AWS::EC2::AvailabilityZone::Name"
},
"Priv1Cidr": {
"Description": "This is the cidr for my appPriv1Subnet",
"Type": "String",
"Default": "10.0.1.0/24"
},
"Priv2Cidr": {
"Description": "This is the cidr for my appPriv2Subnet",
"Type": "String",
"Default": "10.0.3.0/24"
},
"AZ2": {
"Description": "AZ 2 for my network",
"Type": "AWS::EC2::AvailabilityZone::Name"
},
"Pub1Cidr": {
"Description": "Cidr for my appPubSN1",
"Type": "String",
"Default": "10.0.2.0/24"
},
"Pub2Cidr": {
"Description": "Cidr for appPubSN2",
"Type": "String",
"Default": "10.0.4.0/16"
}
},
"Mappings": {},
"Conditions": {},
"Resources": {
"appVpc": {
"Type": "AWS::EC2::VPC",
"Properties": {
"CidrBlock": {
"Ref": "MyVpcCidr"
},
"Tags": [
{
"Key": "Name",
"Value": "AppVpc"
}
]
}
},
"appPriv1Subnet": {
"Type": "AWS::EC2::Subnet",
"Properties": {
"AvailabilityZone": {
"Ref": "AZ1"
},
"VpcId": {
"Ref": "appVpc"
},
"CidrBlock": {
"Ref": "Priv1Cidr"
},
"Tags": [
{
"Key": "Name",
"Value": "Apppriv1subnet"
}
]
}
},
"appPriv2Subnet": {
"Type": "AWS::EC2::Subnet",
"Properties": {
"AvailabilityZone": {
"Ref": "AZ2"
},
"VpcId": {
"Ref": "appVpc"
},
"CidrBlock": {
"Ref": "Priv2Cidr"
},
"Tags": [
{
"Key": "Name",
"Value": "AppPriv2Subnet"
}
]
}
},
"appPubSN1": {
"Type": "AWS::EC2::Subnet",
"Properties": {
"AvailabilityZone": {
"Ref": "AZ1"
},
"VpcId": {
"Ref": "appVpc"
},
"CidrBlock": {
"Ref": "Pub1Cidr"
},
"Tags": [
{
"Key": "Name",
"Value": "AppPubsn1"
}
]
}
},
"appPubSN2": {
"Type": "AWS::EC2::Subnet",
"Properties": {
"AvailabilityZone": {
"Ref": "AZ2"
},
"VpcId": {
"Ref": "appVpc"
},
"CidrBlock": {
"Ref": "Pub2Cidr"
},
"Tags": [
{
"Key": "Name",
"Value": "AppPubsn2"
}
]
}
},
"appIG": {
"Type": "AWS::EC2::InternetGateway",
"Properties": {
"Tags": [
{
"Key": "Name",
"Value": "AppIG"
}
]
}
},
"AttachGateway": {
"Type": "AWS::EC2::VPCGatewayAttachment",
"Properties": {
"VpcId": {
"Ref": "appVpc"
},
"InternetGatewayId": {
"Ref": "appIG"
}
}
},
"appPrivRT": {
"Type": "AWS::EC2::RouteTable",
"Properties": {
"VpcId": {
"Ref": "appVpc"
},
"Tags": [
{
"Key": "Name",
"Value": "AppPrivRt"
}
]
}
},
"PrivRTA1": {
"Type": "AWS::EC2::SubnetRouteTableAssociation",
"Properties": {
"SubnetId": {
"Ref": "appPriv1Subnet"
},
"RouteTableId": {
"Ref": "appPrivRT"
}
}
},
"PrivRTA2": {
"Type": "AWS::EC2::SubnetRouteTableAssociation",
"Properties": {
"SubnetId": {
"Ref": "appPriv2Subnet"
},
"RouteTableId": {
"Ref": "appPrivRT"
}
}
},
"appEIP": {
"Type": "AWS::EC2::EIP",
"Properties": {
"Domain": "vpc"
}
},
"appNatgw": {
"Type": "AWS::EC2::NatGateway",
"Properties": {
"AllocationId": {
"Fn::GetAtt": [
"appEIP",
"AllocationId"
]
},
"SubnetId": {
"Ref": "appPubSN1"
},
"Tags": [
{
"Key": "Name",
"Value": "Appnatgw"
}
]
}
},
"appPrivRoute": {
"Type": "AWS::EC2::Route",
"Properties": {
"RouteTableId": {
"Ref": "appPrivRT"
},
"DestinationCidrBlock": "0.0.0.0/0",
"NatGatewayId": {
"Ref": "appNatgw"
}
}
},
"appPubRT": {
"Type": "AWS::EC2::RouteTable",
"Properties": {
"VpcId": {
"Ref": "appVpc"
},
"Tags": [
{
"Key": "Name",
"Value": "AppPubRT"
}
]
}
},
"PubRTA1": {
"Type": "AWS::EC2::SubnetRouteTableAssociation",
"Properties": {
"SubnetId": {
"Ref": "appPubSN1"
},
"RouteTableId": {
"Ref": "appPubRT"
}
}
},
"PubRTA2": {
"Type": "AWS::EC2::SubnetRouteTableAssociation",
"Properties": {
"SubnetId": {
"Ref": "appPubSN2"
},
"RouteTableId": {
"Ref": "appPubRT"
}
}
},
"appPubRoute": {
"Type": "AWS::EC2::Route",
"Properties": {
"RouteTableId": {
"Ref": "appPubRT"
},
"DestinationCidrBlock": "0.0.0.0/0",
"GatewayId": {
"Ref": "appIG"
}
}
},
"appSG": {
"Type": "AWS::EC2::SecurityGroup",
"Properties": {
"GroupDescription": "Allow ssh port 22 and port 80",
"SecurityGroupIngress": [
{
"IpProtocol": "tcp",
"FromPort": "22",
"ToPort": "22",
"CidrIp": "0.0.0.0/0"
},
{
"IpProtocol": "tcp",
"FromPort": "80",
"ToPort": "80",
"CidrIp": "0.0.0.0/0"
}
],
"VpcId": {
"Ref": "appVpc"
},
"Tags": [
{
"Key": "Name",
"Value": "AppSG"
}
]
}
},
"internalSG": {
"DependsOn": "appSG",
"Type": "AWS::EC2::SecurityGroup",
"Properties": {
"GroupDescription": "Allow traffic from appSG",
"SecurityGroupIngress": [
{
"IpProtocol": "-1",
"SourceSecurityGroupId": {
"Ref": "appSG"
}
}
],
"VpcId": {
"Ref": "appVpc"
},
"Tags": [
{
"Key": "Name",
"Value": "appinternalSG"
}
]
}
}
},
"Outputs": {
"appVpcId": {
"Description": "Id for my vpc ",
"Value": {
"Ref": "appVpc"
},
"Export": {
"Name": "appVpcid"
}
},
"appPrivSN1Id": {
"Description": "Id for my private SN1",
"Value": {
"Ref": "appPriv1Subnet"
},
"Export": {
"Name": "appPrivSNID1"
}
},
"appPrivSN2Id": {
"Description": "Id for my subnet 2 private",
"Value": {
"Ref": "appPriv2Subnet"
},
"Export": {
"Name": "appPrivSNID2"
}
},
"appPubSN1Id": {
"Description": "Id for Public subnet 1",
"Value": {
"Ref": "appPubSN1"
},
"Export": {
"Name": "appPubSNID1"
}
},
"appPubSN2Id": {
"Description": "Id for Public subnet 2",
"Value": {
"Ref": "appPubSN2"
},
"Export": {
"Name": "appPubSNID2"
}
},
"externalSgid": {
"Description": "Id for external security group",
"Value": {
"Ref": "appSG"
},
"Export": {
"Name": "appSGID"
}
},
"internalSGId": {
"Description": "Id for internal security group",
"Value": {
"Ref": "internalSG"
},
"Export": {
"Name": "internalSGID"
}
}
}
}

Answer 1

I suspect 10.0.4.0/16 is a typo that was meant to be 10.0.4.0/24.
The reason is that the cidr 10.0.4.0/16, which you have set for Pub2Cidr starts at 10.0.0.0 and ends at 10.0.255.255, which overlaps with 10.0.1.0/24 which starts at 10.0.1.0 and ends at 10.0.1.255.