AWS ELB Does not Pass Traffic Through to Instance

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votes

I have an ELB configured to listen on port 443, and pass traffic on that port through to an instance on port 443. The ELB is receiving the connection, but the instance behind it does not receive traffic.

What I have checked:

  • ELB answers on 443
  • Instance answers on 443 internally (i.e. telnet localhost 443)
  • Security group for instance is set to allow traffic on 443 from 0.0.0.0/0
  • Security group for ELB is set to allow traffic to flow to instance on 443, as well as from my IP (the latter is definitely working)

Possibly worth mentioning that the instance is in a private subnet, connected to the internet via use of NAT instance and IGW on the public subnet (internet connectivity from the instance works fine).

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amazon-web-servicesamazon
What's the exact 'symptom' you have? What do you observe when you try to browse to the public dns of the ELB on your browser? Does it give you an error message? What does it say? How long does it take to show an error message (under a second? 10-30 seconds?) – Bruno Reis
Try telnet from another server on the subnet to that server is there a respons eof 443. Just thinking down the lines of it being a simple binding or software firewall issue. Also does your instance show as healthy under load balancers in the console, if so, then check your healthcheck is on port 443 and not 80, if on 80, change to 443 and see if it marks as unhealthy. Could you security group for the webserver be stopping the connection from loadbalancer to webserver as remember, SG's both internal and external. Just my 5pence anyway :-) I run 9 ELB/ALB's. – Liam Wheldon
"Try telnet from another server on the subnet to that server is there a respons eof 443." Is this ELB running in HTTP mode? If so, that is normal behavior. If not, please explain the ELB listener and instance port configuration, and whethet this is Classic or ALB. Also, is the instance passing its health check and showing InService on the balancer? – Michael - sqlbot

1 Answers

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Soooo, this turned out to be ghosts, or goblins, or some other unsatisfying explanation :/

After checking everything over and over, I took down the instances, brought new ones up, and it worked. Sorry for those here from Google, I don't know what to tell you.