To switch business internet providers without downtime, install the new circuit while the old one is still running, test it, then move your traffic and services across in a planned order and cancel the old service only after the new one has carried normal business for at least a few days. Nearly every switch that goes wrong skips one of those steps, usually by cancelling first or by forgetting what depends on the old IP addresses.
The fear of a messy cutover keeps many businesses on contracts they know are overpriced. It does not have to. A switch is a small project with a known shape, and most of the work happens before anyone touches a cable.
The principle: overlap, then cut over
The safest switch has a period where both circuits are live. The new one is installed, tested and connected to your firewall while the old one is still carrying everything. You then move traffic across deliberately, with the old circuit available as a fallback, and cancel it once you are sure. Paying for two circuits for a few weeks costs something, but it costs far less than a day with no connection.
Step 1: Check the old contract before ordering the new one
Find the term end date, the notice period and how notice must be given, plus any early termination fee if you are leaving before the end. The aim is to schedule the overlap so that it ends close to the date you can leave without penalty. Our guide to business internet contract terms covers what to look for. Do not send a cancellation yet. Notice of intent to leave is different from cancelling service, and a premature cancellation is the single most common cause of switch-day outages.
Step 2: Make a list of everything that depends on the connection
This is the step that decides whether the switch is quiet or painful. Static IP addresses belong to the carrier, so when you change carriers they change, and anything that knows your old addresses breaks. Go through:
- Firewall and VPN. Site-to-site tunnels to other offices or cloud services, and remote access for staff.
- Allow-lists held by other people. Banks, payment processors, software vendors, clients and government portals that only accept connections from your addresses.
- DNS records pointing at your office: a mail server, a VPN hostname, a camera system, a remote desktop gateway.
- Phones. Hosted or SIP phone services that recognise your office address or registration.
- Cameras, door entry and alarms that report out or are reached from outside.
- Printers and scanners that send email through a mail relay that checks your address.
- Payment terminals and any point-of-sale system that connects outward.
For each, note who controls it and how much notice they need to add a new address. Some external allow-lists take days or weeks to change. More on why addresses behave this way in static IPs and BGP.
Step 3: Order the new circuit with the real lead time
In a building where the new carrier is already lit, plan on 2 to 4 weeks. If construction is needed, plan on 60 to 90 days. Shared fiber and coax where the building already has them can be days. Start from the date you want to be finished and work backwards, adding the overlap period. See fiber installation timelines for what drives each case.
Step 4: Install and test before anything depends on it
When the new circuit is handed over, test it on its own before connecting it to anything important:
- Speed in both directions, at different times of day.
- Latency and packet loss to the services you actually use.
- That every static IP in the new block routes correctly.
- Reverse DNS for the new addresses, if you send email directly.
- That the carrier's support line and ticket process work, before you need them.
Step 5: Connect it as a second line
Most business firewalls can run two internet connections at once. Connect the new circuit as a second WAN while the old one stays primary. Now you can move individual services across one at a time, and fall back instantly if one misbehaves. If you already use SD-WAN, this is routine: the new circuit becomes another path and policies decide which traffic uses it.
Step 6: Add the new addresses everywhere, before removing the old
Where possible, ask every allow-list owner to add your new IP addresses alongside the old ones, rather than replacing them. That way the service keeps working whichever circuit you are on. A day or two before you change any DNS records, lower their time-to-live (TTL) so changes spread quickly when you make them.
Step 7: Move services across, in order
- General browsing and cloud apps first. Lowest risk, easiest to judge.
- Outbound services with allow-lists, once each external party confirms the new addresses are added.
- Inbound services: update DNS for VPN, cameras and anything reached from outside, then confirm from an outside connection.
- Site-to-site VPNs, updating the peer address at the other end at the same time.
- Phones last, at a quiet time, with test calls in and out.
Do the riskier steps outside business hours, with a written rollback: what you will switch back, and how, if something fails.
Step 8: Run on the new circuit, then cancel the old one
Let the new circuit carry normal business for at least a few working days, ideally a full week covering your busiest day. Then cancel the old service in writing, in exactly the form its contract requires, and keep proof. Return any carrier equipment, because unreturned equipment fees are common. Finally, remove the old addresses from allow-lists, so stale permissions do not linger.
If the new circuit is late
Installs slip. Landlord access, building wiring and construction permits are the usual causes. This is exactly why you do not cancel first: a late install with the old service still running is an inconvenience, while a late install after cancellation is an outage. If the delay threatens your old contract's end date, you have three options. Ask the old carrier for a short month-to-month extension, which many will grant at a holdover rate. Bring in a fast temporary connection, such as fixed wireless, 5G or coax where the building has it, to bridge the gap. Or, if the old contract allows it, delay the notice until the new circuit is installed and proven, as in the example below.
Mistakes that cause switch-day outages
- Cancelling the old service before the new one is installed and tested.
- Forgetting an allow-list held by a bank, vendor or client until the day it stops working.
- Changing DNS without lowering the TTL first, so old addresses linger for a day or more.
- Updating one end of a site-to-site VPN but not the other.
- Moving the phones during business hours, with no test calls and no way back.
If your phone numbers are moving too
Internet and phone numbers are separate projects even when the same carrier provides both. Numbers move by porting, which usually takes 2 to 4 weeks and runs on its own paperwork. The rule is the same: do not cancel the old phone service until the port has completed. Our guide to porting business phone numbers covers it step by step.
A planning timeline
| When | What |
|---|---|
| 8 to 12 weeks before (longer if construction) | Check contract dates; order the new circuit; start the dependency list |
| 4 to 6 weeks before | Ask external parties to add the new addresses once you have them; book after-hours windows |
| Install day | Test the new circuit on its own |
| Install + a few days | Connect as a second line; move browsing and cloud apps |
| Following 1 to 2 weeks | Move allow-listed, inbound and VPN services, then phones |
| After a full normal week | Cancel the old service in writing; return equipment; tidy allow-lists |
A worked example
A hypothetical illustration. The office, dates and services are invented.
A 30-person office wants to move from a coax plan to dedicated fiber in a building where the new carrier is lit. Their old contract ends on 30 June with 30 days' notice required. They order the new circuit on 1 May and it is installed on 27 May, tested that afternoon and connected as a second line the next morning. With the circuit proven, they send notice on 28 May, still inside the 30-day window.
Their dependency list has nine items. Seven are under their own control. Two are not: a bank portal that takes ten business days to add a new address, and a client's file transfer server. Both are asked to add the new addresses alongside the old ones as soon as the carrier issues them, before install day. By mid-June everything except the phones runs on the new circuit, the phones move on a Friday evening, and the old service ends on 30 June, after about five weeks of overlap. Nobody in the office notices the switch, which is the point.
Questions to ask your new provider
- When will I receive my new IP addresses, so I can give them to vendors before install?
- Is your network already in my building, and what is the realistic install date?
- Will you hand off to my own firewall, or must I use your equipment?
- Can the term start date be set at install, so I am not paying before I can use it?
- Who do I call during the cutover window if something does not work?
- Can my existing static IP addresses come with me? (Usually not, but ask.)
Let someone else hold the checklist
FiberX puts your address out to several Tier 1 carriers, brings back the best offer, and coordinates the order and install so the overlap is planned rather than improvised. The carrier pays us, so there is no markup, and if your current deal already wins we will say so. Quotes are free with no obligation and you usually hear back the same day. If you want help inside the office during the switch, see managed network and Wi-Fi. Send us your address and current bill, call 478-758-8091 or text (347) 870-0965.
