How to Set Up Automatic Failover (And Know It’s Working)

Automatic failover is one of those things you swear you’ll set up “next week”… right up until the day your primary circuit drops and you discover your backup connection is basically decorative.

If you have an LTE/5G backup, a secondary ISP, or a redundant link at a site, this post will help you set up failover in a practical way—and verify it actually works before you need it.

Failover vs. Load Balancing (They’re Not the Same)

These terms get tossed around like they’re interchangeable. They aren’t.

• Failover means: Primary link runs the show. Backup takes over when primary fails.
• Load balancing means: Traffic is shared across two or more links—either all the time or based on rules.

Both can be useful. But if your goal is business continuity, failover needs to be rock-solid even if you don’t load-balance at all.

If you’re using SD-WAN, failover and load balancing are often part of the design—along with app prioritization and performance monitoring. Fusion Connect’s Managed SD-WAN offering is built around multi-link resilience, so policies can be tuned to what matters most when a link degrades or drops.

Step 1: Confirm You Have the Right Hardware Capabilities

If none of that exists… you may have a backup link, but not a backup strategy.

Step 2: Set Up Health Checks That Actually Reflect “Internet Working”

A common mistake is using a health check that only verifies your ISP gateway is reachable. That can pass even when the internet is effectively down.

Better practice: configure probes to multiple reliable destinations, such as:

• A public DNS resolver (example: 1.1.1.1 or 8.8.8.8)
• A second IP on a different network
• A third destination (optional, but helpful)

Why multiple? Because one target can fail without your whole connection being dead.

General starting point settings:

• Probe interval: 3–5 seconds
• Fail threshold: 3–5 missed probes
• Recovery threshold: 5–10 successful probes

This helps reduce “flapping” (bouncing between links) while still failing over quickly.

If you don’t want link monitoring to be a “hope for the best” situation, this is where ongoing visibility helps. Fusion Connect’s Managed Network Services are positioned around proactive monitoring and support—useful when you want failover behavior validated and watched over time, not only during emergencies.

Step 3: Decide What Should Fail Over (And What Shouldn’t)

In most SMB environments, the simplest approach is: everything fails over.

If you’re standardizing backup connectivity across many locations, Fusion Connect’s Wireless Broadband positioning (LTE/4G/5G, including multi-carrier eSIM options) is designed for situations where you need a consistent approach to cellular backup rather than a one-off hotspot solution.

Step 4: Verify Load Balancing (If You Use It)

If you are load balancing, verify it’s behaving the way you think.

Quick checks:

• WAN usage graphs: do both links show traffic during normal operation?
• Session distribution: are new sessions spreading across both WANs?
• Policy routing rules: are high-priority apps pinned to the best link?

What you’re looking for is consistency, not chaos. If traffic distribution is wildly uneven, it may be configured for failover—not balancing—or your rules are steering more than you intended.

Step 5: Check the Logs (This Is Where the Truth Lives)

Most routers/firewalls will log WAN events. Look for entries related to:

• Link down / link up
• Probe failures
• SLA monitor state changes
• Failover triggered
• Failback triggered

If your device supports event notifications, enable alerts for WAN state changes. Automatic failover is great—but only if you know it happened.

Step 6: Test It (Yes, On Purpose)

Testing failover doesn’t need to be dramatic, but it does need to be real.

Safe test method (recommended):

1. Choose a low-impact window (early morning, after hours, etc.)
2. Confirm someone can monitor:
   • A dashboard view (router/firewall)
   • A live session (voice call, VPN login, POS transaction—whatever matters most)
3. Physically unplug the primary WAN circuit (or disable the interface)
4. Confirm:
   • Backup WAN becomes active
   • Users stay connected (or recover quickly)
   • Critical apps behave as expected
5. Reconnect primary and confirm failback behavior

What to document:

• Time to failover
• Whether any calls/sessions dropped
• Whether DNS or VPN behaved oddly
• Any alerts/log entries

If you’re building your failover plan from scratch—or trying to sanity-check what “good” looks like—Fusion Connect also has a practical overview of backup internet options and how failover typically works in real environments.

Step 7: Know When It’s Not Working

If you see these symptoms, it’s time to escalate—because “mostly works” is not the goal when you’re talking about business continuity.

Bonus: When Cellular Isn’t the Best Backup Path

In some locations, cellular is weak, inconsistent, or constrained by building materials and geography. If you need a physically diverse backup path, satellite internet can be an option.

Fusion Connect positions Starlink Satellite Internet as an alternative or backup connectivity path for businesses that need coverage where other options fall short.

The Bottom Line

A backup connection is only valuable if:

• Failover triggers reliably
• The backup link actually supports your critical workflows
• You’ve tested it—and you can prove it

Because “we have LTE backup” sounds great… until the day you discover you don’t.