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Elastic Load Balancers

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  • Useful Links:

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    • Network introduction

    • Authenticate users

    • Application introduction

    • Classic introduction

    • Elastic Load Balancing: Deep Dive and Best Practices

    • Exam Tips:

      • Need to know what scenario to use specific types of ELBs.
      • Provides abstraction.
      • ELBs allow decoupling of the tiers.
      • ELB is a DNS A record pointing at 1+ nodes per AZ.
      • Nodes (in one subnet per AZ) can scale.
      • Internet facing (public IPv4) load balancers can work with public or private instances.
      • Internal facing IP is private only IPs.
      • Listener configuration controls what the LB listens to.
      • 8+ free IPs per subnet, and /27 subnet to allow scaling.
      • Classic Load Balancer:
        • Not recommended.
        • Not layer 7 device.
        • Can do SSL offloading by having the LB do the SSL/TLS work, freeing up some work on the instances.
      • Application Load Balancers:
        • Recommended LB to use within VPCs.
        • Supports both IPv4 and IPv6 using dual stack.
        • Associate target groups.
        • Understand up to layer 7 in the OSI model.
        • Does allow you to provide multiple success codes.
        • Almost always cheaper.
        • Can make routing decisions via rules:
          • Forward
          • Redirect
          • Authenticate
        • Can cope with multiple certificates.
        • HTTP/2 is supported.
        • Can have Lambda functions as targets.
        • Health checks defined at target group level.
      • Network Load Balancers:
        • Operate at layer 4 of the OSI model.
        • TLS termination supported.
        • UDP and TCP both supported.
        • End-to-end encryption? = NLB
      • Cross-Zone Load Balancing:
        • Allows for more even distribution of loads.