FreeBSD 15: DNS resolver loop between local_unbound and resolvconf

📖 ~1 min read

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution – Primary Fix
7. Solution – Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

DNS queries intermittently fail or time out, impacting package management and service discovery.

Environment & Reproduction

Occurs when local_unbound and resolvconf are configured to reference each other indirectly.

Root Cause Analysis

Recursive forwarding loop prevents successful query resolution and exhausts local resolver capacity.

Quick Triage

Check resolver targets and confirm whether localhost points back through forwarding path.

Step-by-Step Diagnosis

Trace query flow from libc resolver to local_unbound and upstream nameservers.

Solution – Primary Fix

Set authoritative upstreams explicitly and remove cyclic resolver references.

Solution – Alternative Approaches

Use direct external resolvers on servers where local caching is not required.

Verification & Acceptance Criteria

DNS resolution remains stable across repeated lookups and service restarts.

Rollback Plan

Revert resolver configuration files and reload network stack to previous known-good state.

Prevention & Hardening

Apply resolver config linting and monitor recursive query failures for early detection.

Related Errors & Cross-Refs

Common with split-horizon DNS misrouting and VPN DNS override races.

Related tutorial: View the step-by-step tutorial for freebsd-15.

View all freebsd-15 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

local-unbound setup docs, resolv.conf references, and FreeBSD DNS administration notes.