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ERROR_REM_NOT_LIST
This is a redirector-era network error, not a generic statement that the local TCP/IP stack is down. Windows has separate machinery for deciding which provider owns a UNC path. For direct UNC access, the Multiple UNC Provider (MUP) performs prefix resolution and routes the path to a registered redirector; mapped connections are established through MPR and WNet provider DLLs.
The most useful distinction is whether the failure happens while claiming the server/share prefix or after a provider has already accepted it. A UNC path that no provider claims points toward naming, provider registration, or path interpretation. A path that was previously usable and then fails later belongs to connection/session diagnosis instead.
Evidence to capture
- Record the exact UNC path and whether the same server is reachable through another share name.
- Compare direct UNC access with an explicit WNet connection so the provider-selection path is visible.
- Identify the provider that claims the resource; do not treat DNS success alone as proof that the UNC namespace is valid.
- Preserve a provider-specific extended error when a WNet call also reports ERROR_EXTENDED_ERROR.
Windows MUP and UNC prefix resolution · Windows network redirector architecture · Retrieving WNet network errors
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