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Links: 101 AWS SAA Index


  • Managed load balancer by AWS.
  • Serve multiple AZs in the same region. For multi region load balancing we need Route53.
  • ELBs handle failures of EC2 instances by not sending them traffic and provides regular health check of EC2 instances.

    • The health check is done on a port and a route. For example:
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    • If the response is not 200 then the instance is unhealthy and no traffic will be sent to it.
  • ELBs provide SSL termination.

  • Separates public traffic from private traffic.
  • Load balancer security group will receive traffic from anywhere. This security group will be used as an inbound rule by the EC2 instances. Security group referencing.
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    • We use port 80 for EC2 instances since TLS termination happens at load balancer.


  • Elastic Load BalancingĀ provides access logs that capture detailed information about requests sent to your load balancer.
  • Each log contains information such as the time the request was received, the client's IP address, latencies, request paths, and server responses. You can use these access logs to analyse traffic patterns and troubleshoot issues.
  • Access logging is an optional feature of Elastic Load Balancing that isĀ disabled by default.
  • After you enable access logging for your load balancer, Elastic Load Balancing captures the logs and stores them in the Amazon S3 bucket that you specify as compressed files. You can disable access logging at any time.


  • Traffic is encrypted between the client and the load balancer.
  • TLS is the newer version of SSL. To remember T > S.
  • The load balancer performs SSL termination. We use HTTP inside our private VPC.
  • The load balancer uses X.509 certificate.
  • We manage the certificates using AWS Certificate Manager (ACM).


  • Server name indication.
  • It solves the critical problem of loading multiple SSL certs onto one web server.
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  • Supported by ALB and NLB. Not supported by CLB. For SNI in CLB we have to use CloudFront distribution.
  • In order to use SNI, all you need to do is bind multiple certificates to the same secure listener on your load balancer. ALB will automatically choose the optimal TLS certificate for each client.
  • Wildcard certificates can only handle sub domains and not domains.

Last updated: 2022-04-20