AWS::ElasticLoadBalancingV2::LoadBalancer

• Forwards traffic to multiple servers (or EC2 instances)
• Benefits
• Spread load evenly across multiple downstream instances
• Expose a single hostname that balances between of the backends in the target groups
• Handle failure of downstream instances (regular health check)
• SSL termination (HTTPS)
• Enforce stickiness with cookies

Static IPs

• By default the LB is exposed as a hostname that balances between of the backends in the target groups
• Optionally it's also possible to assign an EIP to the Load Balancer and access it via an Static IP
• It's necessary 1 EIP for each AZ in which the LB is deployed
• ALBs do not support EIPs because they operate at Layer 7 and they manage dynamically their networking resources (including Network Interfaces)
• NLBs on the other hand operate at Layer 4 and allow for specific EIP and ENI associations

Properties

• https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-elasticloadbalancingv2-loadbalancer.html

Type: AWS::ElasticLoadBalancingV2::LoadBalancer
Properties:
  EnforceSecurityGroupInboundRulesOnPrivateLinkTraffic: String
  IpAddressType: String
  LoadBalancerAttributes:
    - LoadBalancerAttribute
  Name: String
  Scheme: String
  SecurityGroups:
    - String
  SubnetMappings:
    - SubnetMapping
  Subnets:
    - String
  Tags:
    - Tag
  Type: String

SecurityGroups

• With a LB, the EC2 can have an inbound rule to restricting access only from the LB (instead of allowing from anywhere)

LoadBalancerAttributes

• load_balancing.cross_zone.enabled
• Balance between instances in different AZs
• However, a LB in a region cannot forward load to another region (in this case one LB in each region is necessary)
• With Cross-Zone balancing load is distributed evenly across all instances (in all AZs)
  • It's always enabled for ALB (cannot be disabled). It's free
  • It's enabled (by default) for CLB. It's free
  • It's disabled (by default) for NLB. It's paid
• Without Cross-Zone balancing load is distributed for the AZ, and not for the total of instances itself

Scheme

• LB can be internal or internet-facing

Type

• Application Load Balancer (ALB)
• Network Load Balancer (NLB)
• Gateway Load Balancer (GWLB)

Classic Load Balancer (CLB) is created with AWS::ElasticLoadBalancing::LoadBalancer