Leased line
A leased line is a dedicated internet circuit for one business site, with matching upload and download speeds, no sharing of capacity with neighbouring premises, and a written uptime SLA.
A leased line is an internet circuit installed to your building for that site alone. Standard broadband, including many full-fibre products, shares local capacity with other premises, so speed can fall when neighbouring demand rises. On a leased line the bandwidth you order is yours for the term, with matching upload and download. The contract usually includes a written uptime SLA, which most broadband products don't offer.
In a UK office the circuit arrives at the premises, often over Openreach fibre, then your provider monitors it. You size capacity to how many people and systems are active at once, because cloud applications and phone traffic share that circuit. Installation can need landlord permission and street works, so it takes longer than activating broadband. Once it's live, the provider should watch the circuit around the clock and start work within the SLA response time.
A single fibre into the building is one point of failure, and street works can take the site offline unless a second circuit on a different route is ready. The SLA usually covers the circuit to the premises, not a congested office network or a misconfigured firewall. Oversizing wastes budget. Undersizing means calls and cloud sync compete by mid-morning. If the carrier and the office network sit with different firms, a fault can sit unanswered in two queues.
When it matters
- →Shared broadband slows once neighbouring premises get busy.
- →Staff send large files or run cloud backups during the day.
- →Phone calls now run over the internet and drop when capacity dips.
- →There is no second circuit if the incoming fibre is cut.
Related terms
Leased line: common questions
What is the difference between a leased line and broadband?
Broadband, including most business full-fibre, shares capacity in the local network. Your speed can drop when neighbouring premises are busy. A leased line is assigned to your site alone, so the bandwidth you order is the bandwidth you get during the working day. Upload and download are the same speed, which many broadband products aren't. A leased line also comes with a written uptime SLA and a named response commitment. Broadband is cheaper and usually quicker to install.
How long does it take to install a leased line in the UK?
There's no single lead time. If fibre is already in the building, the provider can often activate a circuit faster than if a new connection has to be built. New fibre can need a survey and landlord permission, called a wayleave. Street works can stall the date too. Ask the provider to survey the address before you treat a catalogue timescale as a plan. Don't set a go-live date in a lease or cloud migration that assumes the circuit will be ready on a set date.
Can a leased line go down?
Yes. Dedicated means the capacity isn't shared with neighbouring premises. It doesn't mean street works or a carrier fault can't take it down. A 99.9% uptime SLA is a target with a named response, not a promise of zero disruption. Wanzo monitors leased lines 24/7 with a four-hour response commitment. You still need a second circuit on a different route if the site has to stay up through a break in the primary fibre.
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