🟡 Medium   ⏱ 5–30 min  Last verified: 20 May 2026
Affected versions: FreeBSD 13

📖 ~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

FreeBSD 13 dual-stack hosts may show IPv6 addresses but fail traffic due to route or policy errors.

Environment & Reproduction

IPv6 pings fail, applications stall on AAAA attempts, and external IPv6 services are unreachable.

Root Cause Analysis

Missing default IPv6 route, disabled acceptance of router advertisements, or blocked ICMPv6 in firewall.

Quick Triage

Run ifconfig, netstat -rn -f inet6, and ping6 gateway; inspect pf rules for essential ICMPv6 types.

Step-by-Step Diagnosis

Capture current IPv6 addresses, route table, and RA status. image_ref=0

Illustrative mockup for freebsd-13 — terminal_or_shell
Inspecting IPv6 addresses and routes from shell — Illustrative mockup — Progressive Robot

Solution – Primary Fix

Set ifconfig__ipv6 and ipv6_defaultrouter via sysrc, reload network, and permit required ICMPv6 in pf. image_ref=1

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Illustrative mockup for freebsd-13 — log_or_config
Reviewing rc.conf IPv6 and router advertisement settings — Illustrative mockup — Progressive Robot

Solution – Alternative Approaches

Restart netif and routing services after updates to apply IPv6 settings correctly.

Verification & Acceptance Criteria

Persist IPv6 parameters in rc.conf and keep SLAAC versus static configuration clearly separated.

Rollback Plan

Allow neighbor discovery and router advertisement traffic in pf to maintain IPv6 reachability.

Prevention & Hardening

Verify ping6 to external targets and successful TCP connectivity over IPv6 paths.

Monitor IPv6 route presence and include dual-stack checks in service probes.

Related tutorial: View the step-by-step tutorial for freebsd-13.

View all freebsd-13 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Consult man rc.conf, man ifconfig, and FreeBSD IPv6 networking chapters.

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