In short
A leased line works by connecting your site to the provider's network over its own fibre access line. Traffic leaves your network through a router, passes the network terminating equipment, travels the dedicated access line to a point of presence on BT's network, and then reaches the internet. Nothing on that access line is shared with other customers.
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The path, step by step
Here is the journey your traffic takes on a BTnet leased line, from the device on your desk to the wider internet:
- Your network (LAN). Laptops, phones, servers and Wi-Fi access points connect to your switches and cabling. This part is yours.
- The router or firewall. Traffic leaves your LAN through a router. With BTnet + Cisco router or BTnet Meraki, BT supplies and manages this equipment. With BTnet wires only, it is your own router or firewall.
- The network terminating equipment (NTE). A small unit, usually wall or rack mounted, where BT's access line ends inside your building. Your router plugs into it.
- The access line (bearer). A dedicated fibre circuit from your building into BT's network. This is the physical connection, and its size, for example 100Mbps, 1Gbps or 10Gbps, sets the ceiling for your speed.
- The port and point of presence (PoP). The access line connects to BT's network at a port on equipment in a point of presence. The port speed is the bandwidth you buy.
- BT's core network. Your traffic is carried across BT's network.
- The internet and cloud services. From BT's network your traffic reaches the internet. For Microsoft, Apple, Google and Amazon cloud services, BT says it uses Direct Private Peering, so that traffic does not cross the public internet.
Return traffic follows the same path in reverse. Because the access line is dedicated and the bandwidth symmetrical, the same capacity is available in both directions.
Bearer and port speed: two numbers that matter
A leased line has two speeds, and they are easy to confuse:
| Term | What it means | Example |
|---|---|---|
| Bearer | The physical access circuit to your site, which sets the maximum possible speed | A 1Gbps Ethernet fibre bearer |
| Port speed | The bandwidth you order and pay for, which can be lower than the bearer | A 200Mbps port on that 1Gbps bearer |
The gap between the two is room to grow. With Bandwidth Flex, BT lets you change the port speed within the bearer's capacity without installing a new line; BT's help pages say flex needs 72 hours' notice and the rental changes pro rata. BT's terms add that each flex is chargeable and must run for at least five Business Days before the next change, and that a flex beyond what your managed equipment can handle means new equipment and a new minimum period. Going beyond the bearer means a bigger bearer. Our guide to leased line bearers explains the options, and BTnet speeds lists the range: port speeds from 2Mbps to 10Gbps.
BT's terms also point out that the throughput you measure will be a little lower than the port speed, typically by 5-10%, because of network and IP overheads. That is normal for any Ethernet connection, not a fault. See our leased line speed test guide.
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Why the line is uncontended
On broadband, many customers' connections are combined and share capacity further into the network, which is why speeds dip at busy times. On a leased line, the access line carries only your traffic and the port speed is reserved for you. BT describes BTnet as 100% uncontended and dedicated, and its terms list uncontended, symmetrical bandwidth as a standard part of the service.
That is also why BT can offer BTnet without a fair usage policy: you can use the bandwidth you pay for as much as you like. See contended vs uncontended for a fuller explanation.
Where the provider's responsibility ends
Every leased line has a service management boundary: the point up to which the provider runs and supports the service. Beyond it, the network is yours. Under BT's terms, the boundary for BTnet depends on how you take it:
| How you take BTnet | Where BT's responsibility ends | What is yours |
|---|---|---|
| With managed equipment (Cisco or Cisco Meraki) | The LAN port on BT's managed equipment | The cable from that port and everything on your LAN |
| Wires only | The network terminating unit (NTU) on BT's access line | The cable to your router, the router or firewall itself, and your LAN |
| Delivered into a data centre | The patch panel in the data centre's co-location room | Ordering the cross-connect from the data centre provider to your equipment |
BT tests a new service over an Ethernet cable and does not connect or test wireless, so Wi-Fi performance is a separate question even where BT supplies the access points through BTnet Wi-Fi. Knowing the boundary helps when something goes wrong: our BT leased line support page explains how faults are reported.
Is BTnet the right fit for you?
We will check it against your systems and requirements and recommend the right option.
Who builds the access line
If there is no suitable fibre into your building already, one has to be built. BT's local access network is managed by Openreach, the BT Group company that looks after the connections between customers' premises and the local exchange, so you may hear from Openreach during the survey and installation. Two things can affect your timeline:
- Excess construction charges (ECC): extra charges where reaching your site needs more engineering than normal. See excess construction charges.
- Wayleaves: permission from the landlord or land owner to install network and equipment in their building or on their land, often needed when you rent your premises. See wayleave agreement.
A site survey confirms the route into your building, where the NTE and equipment will sit, and whether any extra work is needed. BT's help pages say installation can take up to 70 working days, depending on the survey, and BT gives a Customer Committed Date once the survey is done. The BTnet installation process covers each step.
Adding resilience
A single leased line has a single path, so a cable cut or an equipment fault can take the site offline. BT offers three ways to add a second access line to BTnet: failover, where a standby line takes over if the main one fails; load balancing, where both lines run together; and a lower-speed back-up line. BT's terms say availability of each option depends on your configuration, routing protocol, speed and location, and the equipment for the second line connects to the same LAN segment as the first. See resilient BTnet.
Talk it through with us
If you are trying to picture how BTnet would fit into your network, we can help. Forever Communications is an Authorised Supplier for BT: we look at your current setup, where your router and firewall sit, how much bandwidth you need now and later, and whether you need resilience, then prepare a quote around it. Contact us with your postcode and a short description of your site.
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
How does a leased line connect to the internet?
Your router connects to the network terminating equipment, which sits at the end of a dedicated fibre access line. That line runs to a point of presence on the provider's network, which connects your traffic to the internet.
Is a leased line point to point?
The access line runs point to point from your site to the provider's network. A leased line used for internet access, like BTnet, then connects you to the internet rather than to another of your own sites.
What is the NTE on a leased line?
The network terminating equipment is the unit where the provider's access line ends inside your building. On BTnet wires only, BT's responsibility ends there and your router connects to it.
Does a leased line need a router?
Yes. BT can supply and manage a Cisco router or Cisco Meraki equipment with BTnet, or you can take BTnet wires only and use your own router or firewall. See BTnet leased line plans.
What is the difference between bearer and port speed?
The bearer is the physical circuit and sets the maximum speed. The port speed is the bandwidth you buy on it, which you can flex up or down within the bearer. See leased line bearers.
Still have a question about BTnet?
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