🟠 High   ⏱ 5–30 min  Last verified: 20 May 2026
Affected versions: FreeBSD 12

📖 ~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

IPv6 connectivity drops after DHCPv6 renewals because default route disappears from routing table.

Environment & Reproduction

Initial boot has working IPv6, but connectivity fails later after lease renewal or WAN flap events.

Root Cause Analysis

dhcp6c script handling gaps, RA suppression, or race conditions between netif and route updates can remove route.

Quick Triage

Check netstat -rn -f inet6, inspect dhcp6c logs, and verify router advertisements are still received.

Step-by-Step Diagnosis

Trace lease renewal hooks and compare route table changes before and after renewal events. image_ref=0

Illustrative mockup for freebsd-12 — terminal_or_shell
Inspecting IPv6 routes and dhcp6c lease behavior — Illustrative mockup — Progressive Robot

Solution – Primary Fix

Correct dhcp6c hook scripts, ensure accept_rtadv settings align, and restart netif/routing to restore route persistence. image_ref=1

Still having issues? Our IT Solutions & Services team can diagnose and resolve this for you. Get in touch for a free consultation.

Illustrative mockup for freebsd-12 — log_or_config
Reviewing dhcp6c.conf and interface route scripts — Illustrative mockup — Progressive Robot

Solution – Alternative Approaches

Use static IPv6 default routes in controlled environments where dynamic renewals are unreliable.

Verification & Acceptance Criteria

IPv6 default route persists across renewals and end-to-end IPv6 reachability remains stable over time.

Rollback Plan

Revert to previous dhcp6c configuration and restart network stack if updated hooks break connectivity.

Prevention & Hardening

Monitor IPv6 route presence and alert on default route loss to reduce mean time to recovery.

Related symptoms include intermittent DNS AAAA failures, asymmetric IPv6 paths, and fallback to IPv4-only traffic.

Related tutorial: View the step-by-step tutorial for freebsd-12.

View all freebsd-12 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

See man dhcp6c, man ifconfig, and FreeBSD IPv6 autoconfiguration documentation.

Need Expert Help?

If you cannot resolve this yourself, our team offers hands-on Server Management, Managed IT Services, and flexible Support Plans. Contact us today — we respond within one business day.