Symptoms
4G/5G backup stays active after the ONT link is restored.
Use the following observations to establish that this is the specific failure described here, rather than an unrelated outage or different account:
- Failing behavior: 4G/5G backup stays active after the ONT link is restored.
- Comparison to run: Compare active WAN route and fiber link state while keeping both uplinks available.
- Pass condition: Fiber becomes primary again with cellular data use halted.
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:
- Automatic failback threshold not met — investigate this first only if the local state or controlled comparison supports it.
- Fiber DNS probe fails despite link — a second layer that may survive a simple restart and requires a targeted check.
- Sticky session policy retains LTE route — investigate when the first two paths do not account for the observed behavior.
Before Making Changes
Avoid unexpected mobile data charges and keep backup enabled until primary proves stable. 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 active WAN route and fiber link state while keeping both uplinks available. 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 active WAN route and fiber link state while keeping both uplinks available. | 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 | Check fiber WAN health and gateway failover status. | This can expose or rule out automatic failback threshold not met without changing several settings together. |
| Inspect the deeper layer | Review gateway health-check targets and failback hold-down timers. | Use the evidence to separate fiber dns probe fails despite link from sticky session policy retains lte route; do not assume either is proven. |
If the local comparison is inconclusive, keep the current system unchanged while checking whether fiber dns probe fails despite link is consistent with the evidence. If not, investigate sticky session policy retains lte route rather than applying every possible fix.
Use Beginner for reversible checks; use Advanced only when the comparison indicates a deeper fault. 4G/5G backup stays active after the ONT link is restored. Run a harmless test and write down the time, device/account, current status indicators and the exact difference from normal behavior. Compare active WAN route and fiber link state while keeping both uplinks available. Do not erase logs or reset the device yet. Check fiber WAN health and gateway failover status. 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. Trigger only a supported manual recheck of the primary connection. 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. Fiber becomes primary again with cellular data use halted. 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 automatic failback threshold not met, fiber dns probe fails despite link and sticky session policy retains lte route separately. Compare evidence from the working and failing paths, and avoid interpreting a green status indicator as end-to-end proof. Compare active WAN route and fiber link state while keeping both uplinks available. Review gateway health-check targets and failback hold-down timers. 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. Check DNS and route metrics before changing any failover rule. 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. Fiber becomes primary again with cellular data use halted. 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 automatic failback threshold not met as certain before running the comparison: Compare active WAN route and fiber link state while keeping both uplinks available.
- Trying several changes at once, such as modifying fiber dns probe fails despite link and sticky session policy retains lte route simultaneously, which makes the successful change impossible to identify.
- Ignoring the safety boundary: Avoid unexpected mobile data charges and keep backup enabled until primary proves stable.
- Assuming that a status label or progress indicator guarantees the actual action completed; verify the outcome independently.
How to Verify the Fix
Fiber becomes primary again with cellular data use halted.
- Repeat the original failing action under equivalent conditions: 4G/5G backup stays active after the ONT link is restored.
- Run the control again: Compare active WAN route and fiber link state while keeping both uplinks available.
- Check the positive pass condition: Fiber becomes primary again with cellular data use halted.
- 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: Review gateway health-check targets and failback hold-down timers. Check DNS and route metrics before changing any failover rule.
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 active WAN route and fiber link state while keeping both uplinks available.
- Preserve the corrected behavior: Fiber becomes primary again with cellular data use halted.
- 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 automatic failback threshold not met.
Frequently Asked Questions
Does this symptom prove automatic failback threshold not met?
No. Start with the controlled comparison: Compare active WAN route and fiber link state while keeping both uplinks available. Only treat automatic failback threshold not met 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: Review gateway health-check targets and failback hold-down timers. That helps determine whether fiber dns probe fails despite link or sticky session policy retains lte route fits the symptoms.
How do I know the repair actually worked?
Use this outcome, not just an on-screen status message: Fiber becomes primary again with cellular data use halted. Keep a record of the working state for future troubleshooting.