Symptoms
IPv6-capable devices lose access following overnight WAN reconnection.
Use the following observations to establish that this is the specific failure described here, rather than an unrelated outage or different account:
- Failing behavior: IPv6-capable devices lose access following overnight WAN reconnection.
- Comparison to run: Compare delegated prefix and device addresses before and after a scheduled reconnect.
- Pass condition: New IPv6 prefix reaches LAN clients with successful external connectivity.
Why It Happens
A local Wi-Fi icon and a registered optical link are different observations. First determine whether the interruption begins at optical registration, the Ethernet handoff, routing or the application using the connection.
Treat these as competing hypotheses, not confirmed diagnoses. Their implications are different:
- LAN router advertises expired prefix — investigate this first only if the local state or controlled comparison supports it.
- Downstream router misses prefix update — a second layer that may survive a simple restart and requires a targeted check.
- DNS retains obsolete AAAA endpoint — investigate when the first two paths do not account for the observed behavior.
Before Making Changes
Do not publish public device IPv6 addresses or expose management interfaces. Fiber access is a chain: the optical terminal, WAN negotiation, routing and DNS can fail independently. A green Wi-Fi light proves only the local radio is active, not that the provider link is usable. Write down the working configuration and, if available, export settings or create a test-only copy before changing account permissions, routes or file locations.
Make one change at a time, note the original value, and repeat the exact same test after each change. If the new outcome is worse, restore that single setting; a full reset would erase evidence and can create additional problems.
Problem-Specific Diagnosis
Begin with this controlled observation: Compare delegated prefix and device addresses before and after a scheduled reconnect. Record the result and time; a vague report such as “sometimes fails” cannot distinguish the three hypotheses.
| Check | What to do | What the result tells you |
|---|---|---|
| Compare a working path | Compare delegated prefix and device addresses before and after a scheduled reconnect. | If one controlled route works, the failed route is probably specific to a setting, permission, device, or service rather than a total outage. |
| Check the local state | Restart the affected downstream routing service after recording prefixes. | This can expose or rule out lan router advertises expired prefix without changing several settings together. |
| Inspect the deeper layer | Inspect router advertisements and prefix lifetimes against the provider delegation. | Use the evidence to separate downstream router misses prefix update from dns retains obsolete aaaa endpoint; do not assume either is proven. |
If the local comparison is inconclusive, keep the current system unchanged while checking whether downstream router misses prefix update is consistent with the evidence. If not, investigate dns retains obsolete aaaa endpoint rather than applying every possible fix.
Use Beginner for reversible checks; use Advanced only when the comparison indicates a deeper fault. IPv6-capable devices lose access following overnight WAN reconnection. Run a harmless test and write down the time, device/account, current status indicators and the exact difference from normal behavior. Compare delegated prefix and device addresses before and after a scheduled reconnect. Do not erase logs or reset the device yet. Restart the affected downstream routing service after recording prefixes. Confirm the relevant account, cable, selected output, permission or status before saving changes. If it is already correct, leave it alone and proceed; do not force a change just to try something. Check router firmware and DHCPv6-PD support. Change only this one condition after recording the old value. If it does not improve the result, restore the former value rather than layering additional guesses on top. New IPv6 prefix reaches LAN clients with successful external connectivity. Repeat the same comparison used in step one. Record what improved, what remains unchanged and whether a reconnect or normal app restart changes the result. Stop here if the expected outcome is stable. Consider lan router advertises expired prefix, downstream router misses prefix update and dns retains obsolete aaaa endpoint separately. Compare evidence from the working and failing paths, and avoid interpreting a green status indicator as end-to-end proof. Compare delegated prefix and device addresses before and after a scheduled reconnect. Inspect router advertisements and prefix lifetimes against the provider delegation. Focus on logs, state, permissions, protocol negotiation or version support relevant to this failure. Do not collect or share credentials, account tokens or unrelated private content. Test temporary IPv4-only resolution for one device without disabling IPv6 network-wide. Use an isolated or test-only configuration where possible. Keep an explicit rollback path; do not weaken security, replace backup originals or bypass equipment protection to make one test pass. New IPv6 prefix reaches LAN clients with successful external connectivity. Observe the behavior through the original trigger again. If the change does not produce this measurable result, undo that change and escalate with the recorded facts, rather than repeating disruptive reset attempts.Step-by-Step Troubleshooting
Capture the failing state
Check the first reversible condition
Apply the lowest-risk targeted fix
Retest and document
Distinguish the competing root causes
Inspect the deeper system layer
Run a second independent isolation test
Validate stability and rollback readiness
Solution Checklist
Common Mistakes to Avoid
- Treating lan router advertises expired prefix as certain before running the comparison: Compare delegated prefix and device addresses before and after a scheduled reconnect.
- Trying several changes at once, such as modifying downstream router misses prefix update and dns retains obsolete aaaa endpoint simultaneously, which makes the successful change impossible to identify.
- Ignoring the safety boundary: Do not publish public device IPv6 addresses or expose management interfaces.
- Assuming that a status label or progress indicator guarantees the actual action completed; verify the outcome independently.
How to Verify the Fix
New IPv6 prefix reaches LAN clients with successful external connectivity.
- Repeat the original failing action under equivalent conditions: IPv6-capable devices lose access following overnight WAN reconnection.
- Run the control again: Compare delegated prefix and device addresses before and after a scheduled reconnect.
- Check the positive pass condition: New IPv6 prefix reaches LAN clients with successful external connectivity.
- Recheck after a normal restart, reconnection or scheduled cycle only when it is safe and relevant.
A single passing attempt is useful but may conceal intermittent failures. Record whether the fix survives the triggering condition without requiring a daily workaround.
If the Problem Continues
Use the deeper comparison rather than repeating the first steps: Inspect router advertisements and prefix lifetimes against the provider delegation. Test temporary IPv4-only resolution for one device without disabling IPv6 network-wide.
For an ISP escalation, provide the fiber link light state, WAN status, time of failure, and results from one wired client, without sharing passwords or public administrative addresses.
If the issue affects money, alarms, shared business records, or protective power equipment, stop risky experiments and use the official administrator, provider or manufacturer channel.
Prevent Recurrence
- Keep a record of the previously failing condition: Compare delegated prefix and device addresses before and after a scheduled reconnect.
- Preserve the corrected behavior: New IPv6 prefix reaches LAN clients with successful external connectivity.
- Record ONT and gateway firmware versions, cabling positions and WAN status during a healthy period; keep the provider support reference for line-level faults.
- Review configuration or hardware changes that could reintroduce lan router advertises expired prefix.
Frequently Asked Questions
Does this symptom prove lan router advertises expired prefix?
No. Start with the controlled comparison: Compare delegated prefix and device addresses before and after a scheduled reconnect. Only treat lan router advertises expired prefix as a candidate until the evidence supports it.
What if the first two checks do not change anything?
Move to a different layer rather than repeating the same action: Inspect router advertisements and prefix lifetimes against the provider delegation. That helps determine whether downstream router misses prefix update or dns retains obsolete aaaa endpoint fits the symptoms.
How do I know the repair actually worked?
Use this outcome, not just an on-screen status message: New IPv6 prefix reaches LAN clients with successful external connectivity. Keep a record of the working state for future troubleshooting.