Describe How to Troubleshoot Various Response F5N4 Practice Questions (Page 3)

Questions 11–15

1. 11application · medium

   A reverse proxy returns a 502 Bad Gateway for a specific endpoint. The NGINX error log shows 'connect() failed (111: Connection refused) while connecting to upstream'. The upstream service is running and listening on the expected port when tested locally. What is the most likely cause?

   • AThe proxy_connect_timeout is set too low
   • BThe proxy_buffering is disabled, causing the upstream to close the connection
   • CThe upstream is listening on a different IP address than the one specified in proxy_pass
   • DThe keepalive directive is set to 0 in the upstream block
   Reveal Solution Discussion Select an answer first
2. 12application · medium

   You need to diagnose why a specific request is returning a 500 Internal Server Error. The error is intermittent and only occurs for a subset of requests. Which NGINX debugging technique would provide the most detailed information about the request processing?

   • AEnable the debug log for the error_log directive
   • BUse the access log with the $upstream_status variable
   • CRun 'nginx -t' to check the configuration
   • DUse tcpdump to capture traffic between NGINX and the upstream
   Reveal Solution Discussion Select an answer first
4. 13application · medium

   A reverse proxy returns a 504 Gateway Timeout for a long-running report endpoint. The upstream application is processing the request correctly but takes about 90 seconds to respond. The NGINX configuration currently has 'proxy_read_timeout 60s'. You need to allow the request to complete without changing the application. What should you do?

   • AIncrease proxy_read_timeout to 120s for that location
   • BAdd proxy_connect_timeout 120s for that location
   • CEnable proxy_buffering off for that location
   • DSet proxy_send_timeout to 120s for that location
   Reveal Solution Discussion Select an answer first
5. 14application · medium

   A security scan reports that the server is leaking the internal IP address of the backend in the 'Server' header. The response headers show 'Server: nginx/1.24.0' and also include an 'X-Backend-Server' header with the internal IP. You need to hide the internal IP from clients. What should you do?

   • ASet server_tokens off to hide the NGINX version
   • BUse add_header to overwrite the X-Backend-Server header
   • CUse proxy_hide_header to remove the X-Backend-Server header
   • DSet proxy_pass_header to remove the header
   Reveal Solution Discussion Select an answer first
6. 15application · medium

   An NGINX reverse proxy is experiencing intermittent slow responses for a specific endpoint. The upstream server is healthy and responds quickly when accessed directly. You enable the ngx_http_log_module with the '$request_time' variable and see that some requests take over 30 seconds. The upstream access logs show the same requests completed in under 1 second. What is the most likely cause of the delay?

   • AThe upstream server is throttling connections from the proxy
   • BThe client connection is slow, but $request_time measures only the proxy-to-upstream time
   • CThe proxy is waiting for a keepalive connection to become available from the upstream pool
   • DThe proxy_read_timeout is set too low, causing NGINX to retry the request
   Reveal Solution Discussion Select an answer first