Internet Failover in Simple Terms

Internet failover is like having a backup generator for your internet connection. When your primary broadband goes down — whether from a cable cut, exchange fault, or provider outage — your failover system automatically switches to a backup connection, keeping your business online.

The switch happens automatically, usually within 10-30 seconds. In many cases, your team won't even notice the primary connection went down.

Why Every Business Needs Failover

Think about what happens when your internet goes down:

• VoIP phones stop working — no incoming or outgoing calls
• Card payments fail — you can't take customer payments
• Cloud apps go offline — no email, no CRM, no accounting software
• Remote workers disconnect — anyone working from home or on the road loses access
• CCTV goes dark — cloud-connected cameras stop recording

For a typical Northern Ireland business, even one hour of downtime can cost hundreds or thousands of pounds in lost productivity and revenue.

Types of Failover Connections

4G/5G SIM Failover (Most Popular)

A 4G or 5G router with a data SIM provides instant backup when your broadband fails. This is the most popular failover option because it's affordable, easy to set up, and uses completely different infrastructure to your fixed-line broadband.

• Cost: £15-30/month for the SIM + £200-500 for the router
• Speed: 20-50Mbps (4G) or 100-300Mbps (5G)
• Switchover time: 10-30 seconds
• Best for: Most businesses

Secondary Fixed-Line Broadband

A second broadband connection from a different provider, ideally using different infrastructure (e.g., if your primary is BT fibre, use a Virgin Media cable connection as backup).

• Cost: £25-50/month for the second line
• Speed: Same as your primary connection
• Switchover time: Near-instant with dual-WAN router
• Best for: Businesses needing high-bandwidth backup

Starlink Satellite

Starlink as a backup connection is increasingly popular, especially for rural businesses where 4G coverage is poor. It uses satellite technology — completely independent of ground-based infrastructure.

• Cost: £75/month + £449 for the dish
• Speed: 50-200Mbps
• Best for: Rural businesses, sites with poor mobile coverage

Leased Line

A dedicated fibre connection with guaranteed uptime SLA. The most reliable option but also the most expensive. Some businesses use a leased line as primary and broadband as backup, or vice versa.

• Cost: £200-500/month
• Speed: 100Mbps-1Gbps (symmetrical)
• Best for: Businesses that can't afford any downtime

How Failover Works Technically

There are several ways to implement failover:

Dual-WAN Router

The simplest approach. A router with two WAN connections (e.g., one Ethernet for broadband, one SIM slot for 4G/5G). The router monitors the primary connection and automatically switches to the backup when it detects a failure.

SD-WAN

Software-Defined WAN is a more sophisticated approach that can intelligently route traffic across multiple connections. It can even use both connections simultaneously for load balancing, and seamlessly failover without dropping sessions.

DNS-Based Failover

For businesses hosting services (web servers, email servers), DNS failover redirects traffic to a backup server or connection when the primary fails. This is more relevant for hosted services than office internet.

Setting Up Failover: What You Need

• A dual-WAN router or firewall — most business-grade routers support this
• A backup connection — 4G/5G SIM, second broadband, or Starlink
• Different infrastructure — ensure your backup uses different physical infrastructure to your primary
• Monitoring — set up alerts so you know when failover activates
• Regular testing — test your failover periodically to ensure it works

Common Failover Mistakes

• Same infrastructure: Having two broadband lines from the same exchange doesn't help if the exchange fails
• Never testing: If you don't test failover, you won't know it works until you need it
• Forgetting the SIM: Data SIMs can expire or run out of credit if not monitored
• No QoS: Without Quality of Service settings, VoIP calls may suffer on the backup connection