In short
Leased line failover adds a standby access line to your primary connection. Under BT's terms for BTnet, BT configures the secondary line as a standby to the primary, and if the primary fails, traffic routes over the secondary. Equipment for both lines connects to the same segment of your LAN. Availability depends on your site.
Get a quote for BTnet failover
Tell us roughly how many users or sites you have and we will reply by email with options and a quote.
How BTnet failover works
In BT's service schedule for BTnet, failover is one of three resilience options. BT configures a secondary access line as a standby to your primary access line, the principal line that normally carries your traffic. If the primary line fails, traffic routes over the secondary line instead.
- Normal running. All traffic uses the primary BTnet access line. The secondary line is connected and ready, but on standby.
- The primary fails. A fault on the access line, the equipment or the route stops traffic on the primary line.
- Traffic moves. Under the configuration BT sets up, traffic routes over the secondary line so the site can carry on.
- The fault is fixed. The primary line is repaired through BT's normal fault process, and traffic returns to it.
BT's terms ask you to connect the equipment provided for the failover line to the same segment of your LAN as the equipment for the primary line. That way, the devices on your network can reach the internet through either line without being reconfigured.
How quickly traffic moves over, and how sessions such as calls or VPN tunnels behave during the switch, depends on the configuration, the routing protocol and your own equipment. We do not quote switchover times; they are a design question worked through for your site.
Who failover suits
Failover fits businesses that need the site to keep working, close to normal, through a line fault:
- Sites where phones are business critical, such as sales teams, contact centres and reception desks on a cloud phone system
- Head offices whose systems other sites or remote staff depend on
- Sites hosting services, such as remote access, servers published to the internet or site-to-site VPN hubs
- Trading sites where bookings, orders or stock systems cannot wait for a repair
- Organisations with contractual or regulatory expectations of continuity, which want a documented plan rather than reliance on service credits alone
If your site can manage on reduced speed during a fault, a lower-speed back-up line may meet the need for less. If you would rather use both lines every day, look at load balancing.
Failover compared with the other options
| Failover | Load balancing | Back-up | |
|---|---|---|---|
| Second line in normal running | Standby | Carries traffic alongside the primary | Standby |
| Speed of the second line | Set in your order | Set in your order | Lower than the primary |
| During a fault on one line | Traffic routes over the secondary | Traffic can flow over the other line, subject to capacity | Traffic moves to the lower-speed line |
| Equipment on the same LAN segment | Yes | Yes | Yes |
| Typical fit | Carry on close to normal | Use both lines day to day | Keep essentials running for less |
All three are BT options for BTnet and use a secondary access line. Which ones are available at your site depends on your configuration, routing, speed and location, so we confirm the options at quote.
Not sure which option fits? Ask us
Tell us what you need and we will recommend the right option for your organisation, with a quote.
Questions to ask before you order failover
A failover line only helps if it survives whatever took out the first one. These are the questions we work through with you, and the ones worth asking whoever designs your network:
- Do the two lines take separate routes? Lines that share a duct or a street route can fail together. Route separation is confirmed at the site survey.
- Do they enter the building separately? A second entry point, where the building allows it, adds protection against works on one side of the site.
- Is the power resilient? Where BT's equipment is on site, BT's terms make a secure, continuous power supply and back-up power your responsibility. If the comms room loses power, both lines go down together.
- What about your own router or firewall? On BTnet wires only you run the edge equipment. One firewall in front of two lines is still one point of failure.
- How will static IP addresses and VPNs behave? Remote access, allow-listed services and site-to-site tunnels need a plan for when traffic moves to the second line. See static IP addresses on BTnet.
- How will you test it? Agree how and when a failover test can be run, so you know it works before you need it.
What failover does and does not protect
It is worth being precise about what a standby BTnet line covers, so the rest of your plan fills the gaps.
| Problem | Does a failover line help? |
|---|---|
| A fault on the primary access line, such as cable damage | Yes, if the secondary line takes a separate path |
| Equipment failure on the primary line | Yes, where the secondary line has its own equipment, as set out in your order |
| Street or building works that cut both lines at once | Only if the two lines are routed separately |
| Power cut in your comms room | No; both lines and their equipment need resilient power, which BT's terms make your responsibility |
| Failure of your own router or firewall on wires only | No, unless your edge equipment is resilient too |
| A fault on your office network or Wi-Fi | No; that sits on your side of BT's service boundary |
| An outage at a cloud service you use | No; that is outside BT's network and your line |
Getting the most from a failover line
A few habits make a real difference. Keep a record of both lines' references, so a fault on either can be reported quickly. Check that monitoring or alerts on your side tell you when the site is running on the secondary line, because a failover that works perfectly can hide the fact the primary has failed. And once the primary is repaired, confirm traffic has returned to it, so the standby is ready for the next fault.
When you report a fault on the primary line, follow BT's incident reporting procedures and keep the ticket number. The BTnet SLA page explains why the report time and ticket matter for any claim.
Is BTnet failover the right fit for you?
We will check it against your systems and requirements and recommend the right option.
Costs, contract and the SLA
Failover adds a second access line, and that is reflected in the price. Under BT's terms, where resilience uses dual access bearers, service introduction charges apply per bearer, including the secondary line, as do cancellation charges if the order is cancelled before the service goes live. We do not publish prices; the factors are explained in BT leased line cost, and your quote shows the resilient design and its charges together.
On service levels, BT's terms say that where you have a resilience option and a qualifying incident occurs, BT applies the availability credit at the impacted site. The claim process is the same as for any BTnet service; see the BTnet SLA.
If you are weighing up failover for a site, contact us with the address and what must keep working, and we will help you design and quote it.
Why buy BTnet from Forever Communications
Forever Communications is part of Forever Group and an Authorised Supplier for BT. We supply BTnet, BT's dedicated leased line internet service, to businesses, schools, charities and public sector organisations, and we help with each step from first enquiry to go-live.
- The right BTnet option for you: we help you choose a speed, bearer, router and resilience option that fits how your sites actually work, from BTnet plans to BTnet speeds
- A clear quote: BTnet is priced per site, so we check availability at your address and set out what is included; see leased line cost
- Installation managed with you: we explain the survey, any wayleave or construction steps and the installation process, and keep you updated on progress
- Connected services in one conversation: phones with BT Cloud Voice, Wi-Fi, firewalls and backup lines, so the whole set-up is planned together
- Help after go-live: we can help with faults, changes and upgrades, with the support arrangements confirmed in your quote
BTnet is a business service. Service levels, lead times and features are BT's and are confirmed at order.
Frequently asked questions
What is leased line failover?
A resilience design where a second line stands by and takes over if the main line fails. For BTnet, BT configures the secondary access line as a standby, and traffic routes over it if the primary fails.
How fast does BTnet failover switch over?
It depends on the configuration, the routing protocol and your own equipment, so it is worked out in the design for your site. We do not quote switchover times.
Does the failover line need its own router?
BT's terms refer to equipment provided for the failover option and ask you to connect it to the same LAN segment as the primary line's equipment. The exact equipment is set in the order.
Can I test BTnet failover?
Testing is worth planning before you need it. Agree with us at design stage how and when a failover test can be run, so you know the site keeps working on the secondary line.
Is failover the same as diverse routing?
No. Failover describes how the second line is used. Route separation describes the physical paths the two lines take. A good resilient design considers both, and the survey confirms what is possible.
Still have a question about BTnet failover?
Ask us and a member of our team will reply by email.