Why the Next Major Internet Outage Should Change How You Design Your Office

An office survives an internet outage when no single line, box or power socket can take everyone offline: two independent internet paths, a firewall or router that fails over between them automatically, local services that keep working without the internet, and a UPS on the network equipment itself.

This guide treats a major outage as a planning scenario, not a forecast, and shows how to design around it with kit from the store: the Fortinet FortiGate 50G firewall, the TP-Link Omada ER605 multi-WAN router, the TP-Link Archer NX200 5G router, the D-Link DWM-311-G 5G modem and the APC Back-UPS Pro BR900MI.

What fails in a typical office when the internet goes down?

Why is a single internet line a single point of failure?

Microsoft 365, Teams calls, cloud phones, payment terminals and remote access all leave through the same door. If it shuts, the office is open but nobody can work. The fix is not a faster line. A 10 Gbps service with no backup is still one cable, one provider and one piece of equipment at each end. If your office is fast but still feels slow, that is a different problem, covered in Your Internet Is 10Gbps. So Why Is Your Office Network Still Slow?

Dual WAN or SD-WAN: what is the difference?

Dual WAN means a router with two or more internet ports that can share traffic between them and switch over when one fails. The TP-Link Omada ER605 is a compact example: its listing gives it one fixed Gigabit WAN port, one fixed LAN port and three ports that can be set as WAN or LAN, with intelligent load balancing, link backup in timing and failover modes, and online detection. It is price on request and carries 5 years of local warranty per the listing, which makes it a sensible fit for a small office that needs failover rather than deep inspection.

SD-WAN goes further by measuring the quality of each link and steering traffic by application. Fortinet describes its Secure SD-WAN as providing "real-time path monitoring and dynamic steering across broadband, 5G, MPLS", running on FortiOS on its FortiGate firewalls, and the FortiOS administration guide covers performance SLA health checks and link health monitoring for each WAN link. That keeps a Teams call on the healthier link instead of waiting for a total failure.

The Fortinet FortiGate 50G brings NGFW, SD-WAN and VPN into one desktop unit with five Gigabit RJ45 ports. Fortinet rates it at 5 Gbps firewall throughput, 1.1 Gbps threat protection and 4.4 Gbps IPsec VPN. It is listed at S$1,168.80 for hardware only or S$1,819.20 with 1 year of FortiGuard Unified Threat Protection. Size on the threat protection figure, because that is the speed you get with security features switched on. For a broader view of FortiGate in small offices, see our FortiGate for small businesses guide.

Should your backup line be 5G, 4G or a second fibre?

The best backup is the one least likely to fail for the same reason as the main line. A second fibre service from a different provider gives similar speeds but may share building risers or street ducts. A cellular link uses a completely different path into the building, which is why 5G or 4G is a popular second WAN for Singapore offices. Check the plan's data allowance, whether router use is permitted, and whether remote staff will need to connect into the office VPN over that link, before you rely on it.

• TP-Link Archer NX200 5G Router (S$302.50): a standalone 5G router with a micro SIM slot, one Gigabit LAN/WAN combo port, two LAN ports, published WAN failover and two external antenna ports for weak-signal rooms. TP-Link's "up to 4.67 Gbps" is a peak modem rate, not a guaranteed speed. 3 years local warranty per the listing.
• D-Link DWM-311-G 5G NR Modem (S$662.40): a compact metal 5G SA/NSA modem with a single 2.5GbE port, four SMA antenna connectors and a -30 to 70 °C operating range. It hands a clean Ethernet feed to the second WAN port of a firewall, which keeps your security policy in one place. 3 years local warranty per the listing.

Which services should keep working with no internet at all?

Design for a few hours of total isolation. Keep shared files people need daily on a local NAS as well as in the cloud, keep printers on local queues, and make sure the gateway still hands out addresses and resolves local names when the outside world is gone. Cloud and SaaS outages, where your line is fine but a service is not, are a separate problem covered in When a Global Cloud Service Goes Down, Does Your Office Stop Working?, and the wider question of depending on one AI provider is argued in Are Businesses Becoming Too Dependent on ChatGPT?

Why does network equipment need a UPS?

A two-second power dip that a laptop never notices will reboot the fibre terminal, router, firewall, switches and Wi-Fi access points, and the office then waits for everything to boot and reconnect. Putting the network on a UPS keeps it running through short interruptions and gives clean shutdowns in longer ones. The APC Back-UPS Pro BR900MI (S$452.50) is a 900 VA / 540 W line-interactive UPS with Automatic Voltage Regulation, six battery-backed C13 outlets and a 10 ms typical transfer time. Its stepped-approximation output suits routers, switches and NAS units per the listing, and Schneider publishes no runtime table for it, so size against your actual watts. Plan for battery replacement: the listing gives a 3 to 5 year expected battery life.

For sizing, see our UPS size calculator guide; for ageing batteries, Your UPS Battery Might Be Dead Before You Realise It; and for the business case, mitigating power outages with APC UPS.

How do you know the failover actually works?

Test it on purpose. Once a quarter, unplug the main WAN during a quiet hour and check that calls, cloud apps and VPN users move across, then plug it back and check traffic returns. Switch the UPS to battery and time how long the network stays up. Set alerts so someone knows when the office is running on the backup link, because a failover nobody notices can quietly use up a data allowance. Back up the firewall configuration and treat firmware updates with the care described in The Next Big Software Update Could Break Your Meeting Room. Are You Prepared? If replacement hardware has a lead time, plan spares early, as discussed in Why a Global Shipping Disruption Can Delay Your Next Office Upgrade, and retire unsupported devices on schedule, as covered in Is Your Business Ready for the End of Another Popular Operating System?

Buy the second path before you buy the faster first one. A backup link you have tested is worth more than extra speed on a line that can still fail.

Buying firewalls, 5G routers and UPS in Singapore

SourceIT supplies Fortinet, TP-Link, D-Link and APC with local warranty. Prices are as listed on 24 October 2026, the ER605 is price on request, and all items above were in stock at the time of writing. Browse Fortinet FortiGate firewalls or the APC UPS collection. Tell us your user count, internet services and what must stay online, and we will suggest a design: use Request for Quotation on the product page, call (65) 6978 3502, email Sales@sourceit.com.sg or use our contact page. Government buyers can reach us through GeBIZ (Vendors@Gov registered).

Frequently asked questions

What is dual WAN failover? A router or firewall with two internet connections that moves traffic to the second one when the first fails. Many also share traffic across both while both are up.

Is 5G good enough as a backup for office fibre? For keeping email, calls and cloud apps running, often yes, depending on signal and plan. Check data allowance and router use with your telco, and test it.

What is the difference between dual WAN and SD-WAN? Dual WAN switches or balances between links. SD-WAN, as on FortiGate, monitors link quality and steers traffic by application across broadband, 5G and other links.

Which network equipment should be on a UPS? The fibre terminal, router or firewall, core switches, PoE switches feeding Wi-Fi access points, the 5G router and any NAS. Size the UPS on their combined watts.

Does a backup internet line protect against cloud outages? No. If the cloud service itself is down, a second line does not help. Offline files and local copies of critical data do.

How often should we test internet failover? At least quarterly, and after any firmware update or change of internet provider, by unplugging the main line during a quiet period.