About the demarc, and who wires past it
Where the provider’s responsibility stops, who runs the wiring from there to your desks, and which side of that line a fault sits on.
What is a demarc?
The demarcation point, or demarc, is where the provider’s network ends and your building’s wiring begins. It’s often a box or panel in a telecommunications room, basement, or riser.
The demarc marks the boundary between the provider’s network and your inside wiring. Your service agreement determines who is responsible for each side.
| Provider side | Your side | |
|---|---|---|
| Who pays | Included with your service | You or your IT contractor |
| Who fixes a fault | Your provider, under your agreement | You arrange it |
| Typical scope | Street to the demarc | Demarc to your switches, desks, and phones |
Why does the demarc matter?
When a provider installs service at your address, that doesn’t necessarily mean the connection reaches your desks.
For example, the provider may bring the connection to a demarc in the basement while your office is on the third floor. Someone still needs to run wiring between the two.
Who wires past the demarc?
Depending on the building and provider, you may have several options:
- Some providers offer inside wiring or an extended demarc for an additional charge.
- Your building may already have usable riser wiring.
- You can hire a cabling or IT contractor to extend the connection.
- In a multi-tenant building, the landlord may control the riser and require an approved contractor.
If your equipment is not near the demarc, the wiring between the two sits on your side of the boundary. Settling who runs it before installation day keeps the connection from stopping in the basement.
Why does it matter when something breaks?
When you report a fault, the provider may test the service up to the demarc. If the service is working there, the problem may be with your inside wiring or equipment.
Knowing where the demarc is tells you which side of the connection needs attention. See service outages.
Last reviewed September 14, 2026
