AWS - Elastic Load Balancing
A Network Load Balancer is configured with a TCP listener on port 80, but clients report connection failures. What is the most likely cause?
A Network Load Balancer is configured with a TCP listener on port 80, but clients report connection failures. What is the most likely cause?
medium📝 Debug Q7 of 15
Step-by-Step Solution
Solution:
Step 1: Verify NLB protocol support
NLB supports TCP listeners on any port, including 80.Step 2: Check network access controls
Connection failures often result from blocked ports in security groups or firewalls.Final Answer:
Port 80 TCP listener is blocked by security groups or firewall -> Option BQuick Check:
NLB TCP port blocked = connection failure [OK]
Quick Trick: Check security groups if NLB TCP connections fail [OK]
Common Mistakes:
MISTAKES- Thinking NLB disallows TCP on port 80
- Expecting HTTP listeners on NLB
- Confusing UDP support
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