load balancer cloudformation sample template

load-balancer.yml

 PrivateLoadBalancerSG:
  Type: AWS::EC2::SecurityGroup
  Properties:
    GroupDescription: Access to the private facing load balancer
    VpcId: !Ref Vpc
    SecurityGroupIngress:
      - SourceSecurityGroupId: !Ref 'PublicEC2InstanceSecurityGroup' # only accept traffic from public accessible instances in the security group
        IpProtocol: -1
    SecurityGroupEgress:
      - CidrIp: 0.0.0.0/0
        IpProtocol: -1

  PublicLoadBalancer:
    Type: AWS::ElasticLoadBalancingV2::LoadBalancer
    Properties:
      Scheme: internet-facing
      LoadBalancerAttributes:
        - Key: idle_timeout.timeout_seconds
          Value: "30"
      Subnets:
        - Fn::ImportValue: PublicSubnetA
        - Fn::ImportValue: PublicSubnetB
      SecurityGroups: [!Ref "PublicLoadBalancerSG"]