unix
9 minDNS Troubleshooting: Trace Name Resolution Before Blaming the Network
Separate resolver configuration, caching, search domains, authoritative records, and application-level DNS behavior.
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4 matching resultsArticles and interview answers
kubernetes
18 minKubernetes Advanced Operations: Packet Paths, Rollouts, DNS, and Operators
Trace service traffic, prevent rollout 502s, debug CPU throttling and CoreDNS, and design conflict-safe controller reconciliation.
Q&A
Q&AHow can you tell a DNS failure from a TCP connectivity failure?
Resolve the name from the failing runtime, then test the returned address and port separately.
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Use the system resolver path, for example getent hosts, and compare with a direct DNS query. If a correct address resolves but the connection fails, investigate route, listener, firewall, or protocol behavior. Run diagnostics inside the same container or namespace as the application because resolver configuration may differ.
unix
11 minTCP, UDP, ss, netstat, and tcpdump: A Layered Network Debugging Guide
Diagnose connection failures by separating DNS, routing, transport, listening sockets, and application protocol behavior.