The Short Version
- Cheapest backup: a $30/month prepaid LTE plan + cellular modem, manual cutover — around $50 total
- Budget automatic failover: dual-WAN router ($120-250) + second ISP or LTE modem — $40-100/month extra
- Prosumer setup: Peplink Balance / UniFi UDM SE + cable + fiber or 5G — $200-400/month total
- Seamless calls during failover requires more than just dual-WAN — you need session persistence or a VPN
What Failover Actually Buys You
Failover isn't just "the internet works when the first line dies." There are three tiers of failover quality:
- Manual failover. When the main line fails, you plug a different cable or switch networks. Takes 30-60 seconds. Your Zoom call drops and has to reconnect.
- Automatic failover. A dual-WAN router detects the failure and routes through the backup within 5-15 seconds. Your Zoom call still drops but reconnects faster.
- Session-persistent failover. Your public IP stays stable (via VPN, SD-WAN, or a bonded solution), so TCP sessions don't die. Your Zoom call flickers but doesn't disconnect.
Most WFH setups only need tier 2. Tier 3 is for people who literally cannot drop a call — stock trading, live broadcast, emergency services.
Backup Connection Options
| Option | Monthly cost | Hardware | Typical speed | Good for |
|---|---|---|---|---|
| Prepaid LTE hotspot | $30-50 | $50-150 | 20-100 Mbps | Light backup, email, calls |
| Unlimited 5G home | $50-70 | Included | 100-400 Mbps | Full replacement, maybe too much for backup |
| Second wired ISP (DSL, cable, fiber) | $40-80 | Included | Varies | Best reliability if two networks exist at address |
| Starlink | $80-120 | $349-599 | 50-200 Mbps | Rural, no cable/fiber option |
| Neighbor Wi-Fi (with agreement) | $0-30 chip-in | Directional bridge ~$150 | Depends | Ultra-cheap emergency backup |
Dual-WAN Router Options
Budget ($100-250)
- TP-Link ER605 / ER7206: $70-150, dual-WAN, solid for home office, load-balance or failover
- Mikrotik hEX / RB5009: $70-220, unlimited capability but steeper learning curve
- OpenWrt router (Linksys WRT3200ACM, GL.iNet Flint): $150-250, dual-WAN via mwan3 package
Prosumer ($300-700)
- Peplink Balance 20X / 30: $500-700, the gold standard for SMB failover, SpeedFusion for session-persistent failover
- Ubiquiti UDM SE / UDR: $400-500, built-in dual-WAN, works with UniFi ecosystem
- Firewalla Gold SE / Gold Plus: $500-700, easy iOS app setup, dual-WAN included
Enterprise (add a zero)
Cisco Meraki MX series, Fortinet, Palo Alto. Not worth the money for a home office unless you already manage them for work.
The $80/Month Starter Build
- Keep your existing cable/fiber primary ($60-100/mo, already paid)
- Add a prepaid LTE hotspot: Visible, US Mobile, or Calyx ($30-45/mo unlimited)
- Buy a TP-Link ER605 dual-WAN router ($80) or use a UniFi Dream Router if you already have UniFi
- Plug primary ISP into WAN1, LTE hotspot (in bridge mode or via Ethernet-out) into WAN2
- Configure failover mode in the router admin — failover triggers on ping loss to 1.1.1.1 or 8.8.8.8 every 10-30 seconds
- Test by unplugging the primary ISP cable; should cut over in 10-15 seconds
Session-Persistent Failover (Tier 3)
Standard dual-WAN routers give you a new public IP on the backup line, which breaks active TCP sessions. To keep calls alive during cutover you need one of:
- VPN to a cloud endpoint (Tailscale, Cloudflare WARP, self-hosted WireGuard on a $5/mo VPS). The VPN's IP stays the same across ISPs, so sessions survive.
- SD-WAN bonding appliance like Peplink's SpeedFusion. Your device sees a single virtual connection that spans both ISPs.
- SIP or Zoom cloud session continuity features — some services reconnect to the same session ID within seconds.
For most WFH needs, a Tailscale exit node or WireGuard on a VPS gets you tier-3 failover for $5/month and an afternoon of setup.
Failover Gotchas
- Router still has the same LAN IP, but your public IP changes — inbound services (self-hosted VPN endpoint, Plex) stop working until main ISP returns. Dynamic DNS updates help but aren't instant.
- CGNAT on LTE / 5G — your backup probably has no reachable public IP. You can still do outbound traffic, just not host anything.
- Metered backup data caps — some LTE plans throttle after 15-50 GB. Make sure the backup is truly unlimited, or have a limit alert set.
- Failover detection tuning — too aggressive and brief packet loss triggers unnecessary cutovers; too slow and you're offline for 60 seconds. 10-30 second probe interval, 2-3 failed probes is a good default.
- Fallback to primary — when primary returns, does your router flap back immediately, or wait to confirm stability? Set a 2-5 minute stability window to avoid thrashing.
Testing Your Setup
- Start a Zoom call with a co-worker
- Unplug the primary WAN cable
- Time how long until the call reconnects or recovers
- Plug it back in, confirm you return to primary
- Repeat from the LTE side — unplug LTE, confirm nothing breaks
Do this once a month. A backup you've never tested isn't a backup — it's a guess.