DNS resolution fails for hostnames from within pods. CoreDNS pods are not running, DNS queries timeout, or upstream DNS is unreachable.
This error occurs when pods cannot resolve hostnames to IP addresses via DNS. Kubernetes uses CoreDNS to provide DNS services. When DNS is unavailable, misconfigured, or upstream resolvers are unreachable, hostname resolution fails and pods cannot communicate with services.
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Additional notes and platform-specific considerations.
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Fifth diagnostic step