Your business needs a backup internet connection if an hour offline costs more than the backup circuit costs in a year, or if phones, card payments and cloud systems all stop when the internet does. The design that works is a second circuit on a physically different path, with automatic failover. A small office that can keep working from mobile phones for an afternoon often does not need one.
The honest answer depends entirely on what downtime costs you, and most businesses have never worked that number out. So start there.
Do the arithmetic first
Your hourly downtime cost is roughly:
- Revenue per working hour multiplied by the share of it that stops without internet. For many businesses that is nearly all of it, because payments, bookings, phones and email ride the same circuit.
- Plus staff cost per hour for people who cannot work.
- Plus anything contractual: missed deadlines, penalties, or orders that go to a competitor.
Then compare it with the yearly cost of a second circuit.
A worked example
Hypothetical numbers for illustration only.
A dental practice takes in about $1,500 an hour on a working day, and its scheduling, imaging and card terminals are all cloud-based. Say 80% of that stops without internet, and eight staff at an average of $40 an hour sit idle. That is about $1,200 plus $320, or roughly $1,500 an hour. If a backup circuit cost, say, $150 a month, a year of backup would cost $1,800, a little over one hour of downtime. One four-hour outage in a year and the backup has paid for itself more than three times.
A four-person consultancy that works from laptops and phones, takes no payments and hosts nothing might lose $200 of productivity in the same outage. The backup costs more than it saves.
Backup options compared
| Option | Strengths | Watch for |
|---|---|---|
| Coax under a fiber primary | Inexpensive, usually a different physical path and network | Low upload; best-effort support |
| Second fiber from another carrier | High capacity; can carry the full office | May share a conduit or building entry with the primary |
| Fixed wireless | No cable into the building at all, so a street cut does not touch it | Needs line of sight and roof access |
| 4G/5G failover | Fast to install, low cost, fully separate from wired networks | Data limits, variable speed, usually no inbound static IP |
| Two circuits with BGP | Your own IP addresses stay reachable on either carrier | Needs network engineering; see static IPs and BGP |
The standard small-to-mid-size design is a fiber primary with a coax or fixed-wireless backup on a physically diverse path, tied together with SD-WAN so failover happens automatically, often in under a second.
Diversity is the whole point
Two circuits from two carriers that enter your building through the same conduit are not redundant. One backhoe takes out both. Diversity has several layers, and each one matters:
- Building entry. Do the two circuits come in through different conduits, ideally on different sides of the building?
- Street route. Do they run down different streets, or share a trench for the last few blocks?
- Carrier network. Is the backup delivered by a different network, or does one carrier lease the other's last mile? Two brands on one physical cable fail together.
- Inside the building. Do both terminate in the same telecom room, on the same power circuit?
Ask specifically how each circuit enters the building and whether either is delivered off-net. A carrier that cannot answer is not a carrier you should rely on for diversity.
Why coax works well as a backup
It is inexpensive, and it usually arrives on genuinely different infrastructure from fiber. You are not buying it for its speed. You are buying it because it is unlikely to fail at the same moment and for the same reason as your primary. See our coax internet page.
How failover works
A backup circuit is only useful if traffic moves to it. There are two common approaches:
- A dual-WAN router or firewall that detects when the primary stops responding and sends traffic out the backup. Simple and inexpensive. Detection can take seconds to minutes, and active calls usually drop.
- SD-WAN, which uses both circuits all the time, measures them continuously and moves each application to the healthier path, often in under a second. See SD-WAN explained.
What can break at failover
Your public IP address usually changes when traffic moves to the backup circuit, because each circuit has its own addresses. Anything that depends on your IP needs a plan: VPN tunnels to other offices, partners that allow-list your address, and anything you host. Common fixes are allow-listing both circuits' addresses, using SD-WAN or a cloud gateway that presents a stable address, or BGP for businesses with the staff to run it.
Do not forget power
If the power fails, both circuits go down with it unless the router, firewall, switches and the carriers' equipment in your suite are on a battery backup (UPS). A second circuit is no use if the box it plugs into is dark.
How big does the backup need to be?
Not as big as the primary. A backup exists to keep the business running, not to deliver a normal day. Size it for the traffic that has to keep flowing during an outage:
- Phones and card payments, which use very little bandwidth.
- The core cloud applications people cannot work without.
- Video calls, if client meetings cannot be moved.
Leave out things that can wait, such as cloud backups, software updates and large uploads. A good SD-WAN or firewall policy can hold those back automatically while the office runs on the backup. For many offices, a backup at a fraction of the primary's speed is plenty. Our guide to how much bandwidth your business needs shows how to estimate the critical load.
Protecting the phones specifically
If your phone system is hosted in the cloud, an internet outage stops calls reaching your desk phones, but the calls themselves can still be answered elsewhere. Most hosted phone platforms can forward calls automatically to mobiles or another office when your site's phones go offline. Set this up and test it; it costs little and protects the calls even when you have no backup circuit at all. A backup circuit plus forwarding covers both the office and the callers.
When you probably do not need one
A small office where work continues on phones for an afternoon, with no payment processing, no hosted services and no scheduled deliveries, is spending money on insurance against an inconvenience. Say so out loud rather than buying it reflexively.
We would rather tell you your risk profile does not justify a second circuit than sell you one you will never use.
The middle option people forget
If a full second circuit is hard to justify, a 4G/5G failover device covers the "cannot take payments" scenario for a fraction of the cost. It will not carry your whole office on a video-heavy day, but it keeps card terminals, the booking system and a few laptops working.
Know when you are running on the backup
Good failover is quiet, which creates its own problem: the primary can be down for days without anyone noticing, because everything still works. Meanwhile you have lost your redundancy, and a second failure takes you offline. Make sure something alerts a person when the primary drops: an SD-WAN dashboard, a monitoring service, or at minimum an email from the firewall. Then treat a primary outage as a ticket to open with the carrier straight away, even if nobody in the office felt it. If the backup is 4G/5G, running on it for days can also use up the data allowance.
Test it, or it does not exist
Failover that has never been tested is a guess. Unplug the primary on a quiet afternoon once a quarter and watch what happens: do calls survive, do card terminals reconnect, does the VPN come back, does anyone get alerted? Fix what breaks while it is cheap to fix.
Questions to ask your carrier
- How does each circuit physically enter the building, and do they share any conduit?
- Is either circuit delivered over another provider's last mile?
- Does the backup come with a static IP, and can my firewall use it for inbound services?
- If I use 4G/5G, what are the data limits and what happens when I exceed them?
- Who monitors failover, and will anyone tell me when I am running on the backup?
- If both circuits are yours, can the primary and backup be priced together?
Get a backup designed around your building
We price the primary and the backup together across several carriers, and check that the two really take different paths into your building. If your numbers say you do not need a backup, we will tell you that too. The quote is free with no obligation, and we usually respond the same day. See Dedicated Internet Access and managed network services, send us your address, or call 478-758-8091 or text (347) 870-0965.
