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·  There are three types of Load Balancers in the AWS offering (Our focus is on Classical Load Balancer) specifically for this article.



  • An Internet-facing load balancer has a publicly resolvable DNS name
  • Domain names (for content on the EC2 instances served by the ELB) is resolved by the internet DNS servers to the ELB DNS name
  • There are three types of Load Balancers in the AWS offering (Our focus is on Classical Load Balancer)
  • Classical load balancer (ELB) supports:
  • HTTP, HTTPS, TCP, SSL.
  • Protocol Ports: 1-65535
  • It supports IPv4 (IPv6 and Dual Stack for others)
  • An ELB listener is the process that checks for connection requests.
  • You can configure the protocol/port on which your ELB listener listens for connection request.
  • Frontend listeners check for traffic from client to the ELB.
  • Backend listeners are configured with protocol/port to check for traffic from the ELB to the EC2 instances.
  • It may take some time for registration of EC2 instances under the ELB to complete.
  • Registered EC2 instance are those that are defined under the ELB (NOT AUTOMATIC).
  • You start to be charged hourly (also for partial hours) once your ELB is active.
  • ELB has nothing to do with the outbound traffic that is initiated from the registered EC2 instances destined to the internet or to any other instances within the VPC.
  • ELB only has to do with inbound traffic destined to the EC2 registered instances (as the destination) and the respective return traffic.
  • If you do not want to be charged or you do not need the ELB anymore you can delete it.
  • Before you delete the ELB, it is recommended that you point the Route53 (or DNS Server) to somewhere else other than ELB
  • Deleting the ELB does not affect or delete the EC2 instance registered with it.
  • ELB forwards traffic to eth0 of your registered instances.
  • In case the EC2 registered instance has multiple IP address on eth0, ELB will route the traffic to its primary IP address.
  • You can add tags to your ELB
  • CLB (ELB) support IPv4 address only.

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