What is a leased line?

A leased line in one paragraph

A leased line is a private, dedicated connection between your premises and a network provider's core network. Nobody else's traffic travels over your access line, the speed you pay for is reserved for you at all times of day, and the upload speed is the same as the download speed. Most UK businesses that talk about a leased line today mean a dedicated internet connection: the line carries your traffic into the provider's network and out to the internet.

The word "leased" is a hangover from the days when businesses rented a fixed circuit from a telecoms company for their exclusive use. You still do not own the line: you pay to use it for a contract term, and the provider builds, owns and maintains it. What has changed is the speed and the technology. Modern leased lines run over fibre and use Ethernet, the same technology as your office network, which is why speeds come in steps such as 100Mbps, 1Gbps and 10Gbps.

What makes a leased line different

Four things separate a leased line from an ordinary business broadband connection:

• Dedicated. The access line from your building is yours alone. With BTnet, BT describes the service as 100% uncontended and dedicated. See contended vs uncontended.
• Symmetrical. You get the same speed up as down, which matters for video calls, cloud backup, CCTV and sending large files. See symmetrical internet speeds.
• Service levels. The contract sets out commitments on availability, delivery and often latency, with service credits if they are missed. See the BTnet SLA.
• Built for your site. A leased line is surveyed and installed for one address, so it takes longer to arrive than broadband but is engineered for business use.

There are trade-offs too: a survey, a longer lead time, a minimum contract period and a higher cost than broadband. We set those out honestly in advantages and disadvantages of a leased line.

BTnet: a leased line in practice

BT sells its business leased line under the name BTnet, and files it under the heading dedicated internet access. Under BT's terms, every BTnet service includes:

• An access line from your site, finished either on equipment BT manages or on BT's network terminating equipment if you choose wires only
• Uncontended, symmetrical bandwidth at the port speed you order
• Port speeds from 2Mbps to 10Gbps, in steps based on Ethernet speeds
• Static IPv4 addresses, plus static or dynamic routed IP addresses
• BT's Business Premium Care support level
• Cleanfeed filtering as standard, which blocks a list of illegal child abuse sites maintained by the Internet Watch Foundation; you can opt out in writing

BT's help pages add that there is no fair usage policy on BTnet, so you can use as much data as you need. You can take BTnet with a fully managed Cisco router, with managed Cisco Meraki equipment and BTnet Security, or as BTnet wires only with your own router or firewall. Our BTnet leased line plans page compares the three, and what is a BT leased line goes into BTnet in more depth.

Who needs a leased line?

A leased line earns its keep when the connection is shared by many people, devices or systems, or when the business stops working if it is slow or down. Typical signs you have outgrown broadband:

• Video calls break up or freeze when several people are on calls at once
• Cloud apps, file sync or Microsoft 365 slow down at busy times of day
• Backups or large uploads run overnight because the upload speed is too low
• You are moving phones to the cloud and want call quality you can depend on
• CCTV, card terminals, building systems and guest Wi-Fi all share one connection
• You need fixed IP addresses for VPNs, remote access or allow-listing with suppliers
• You run more than one site and want consistent internet access at each

Our what is a leased line used for guide covers the common uses, and leased lines by sector looks at schools, healthcare, law firms, manufacturing, retail, hotels, offices, councils and charities.

Leased line or lease line?

You will see both. Leased line is the correct term, because the line is leased from the provider for your exclusive use. "Lease line" is a common misspelling of the same thing, and "leased circuit" or "dedicated line" are older names you may still hear. People also say "Ethernet leased line" or "fibre leased line", which describe the technology rather than a different product.

One distinction does matter. A leased line used for internet access, like BTnet, is often called dedicated internet access (DIA). A private circuit that links two of your own sites without going to the internet is a different kind of service. See dedicated internet access explained for the difference.

How it compares with broadband and full fibre

The headline difference is dedicated versus shared. Broadband, including full fibre (FTTP), shares network capacity between many customers and is normally sold on a best-efforts basis. A leased line reserves capacity for you and comes with service levels.

Read leased line vs broadband and leased line vs FTTP for the detail, and how does a leased line work for the path your traffic takes.

What a leased line costs, and how to get one

There is no single price, because each leased line is designed for a particular address. The cost depends on the bearer and port speed, the contract term, the equipment option, any resilience or security, and how much work is needed to reach your building. Our BT leased line cost guide explains each factor.

Getting one starts with an availability check and a quote, followed by a site survey once you order. Check BTnet availability explains how that works, and the BTnet installation process walks through every step to go-live.

Forever Communications is an Authorised Supplier for BT, and BTnet is what we supply. Tell us your postcode and what you use the connection for, and we can help you work out the right speed, plan and options, check what is available at your address and explain each step before you commit. Contact us for a quote, or read why buy BTnet from Forever Communications.