The platform is up, but one dependency path is not.

Use this when Linux hosts reach targets by IP and keep failing on names because the resolver path shifted under the host. These issues are easy to misread because the operating system still responds while one control path, runtime dependency, or trust assumption is already out of alignment.

The symptom usually appears downstream from the real change.

• Linux assumptions are often changed indirectly by updates, policy, hardware changes, or cleanup work that looked harmless at the time.
• systemd-resolved assumptions are often changed indirectly by updates, policy, hardware changes, or cleanup work that looked harmless at the time.
• DNS assumptions are often changed indirectly by updates, policy, hardware changes, or cleanup work that looked harmless at the time.
• Search Domains assumptions are often changed indirectly by updates, policy, hardware changes, or cleanup work that looked harmless at the time.