system

Demarcation Point (Demarc)

The boundary where the service provider's network ends and the building owner's responsibility begins.

What is Demarcation Point (Demarc)?

The demarcation point — "demarc" — is the physical boundary between the ISP's outside plant and the building's inside cabling. Everything on the provider's side is their maintenance responsibility; everything on the owner's side is yours (and your contractor's). In practice the demarc usually lives in the entrance facility near the MDF. Knowing where it sits matters during construction because pathways, power, and grounding for the carrier's equipment must be coordinated before walls close, and because every new circuit the building orders later will originate there.

Frequently asked questions

The service provider owns their equipment up to the demarc; the building owner is responsible for everything beyond it. That is why clean, labeled, standards-based inside plant matters — once a circuit crosses the demarc, it is your system.

The service provider usually owns the equipment up to the demarcation point. The building owner is responsible for the cabling past it.

It is typically in or near the entrance facility, where the provider's service enters the building.

Published references

Use the current project documents and adopted code. These links identify the standards owner, regulator, or manufacturer behind this article.

Where EIG PRO uses this

structured cabling

networking

commercial

multifamily

Related terms

Entrance Facility

The point where the service provider's cabling (ISP fiber, phone entry) enters the building and meets the inside infrastructure.

Backbone Fiber

The fiber-optic runs that connect IDFs to the MDF and form the high-speed network spine of a building.

MDF (Main Distribution Frame)

The central networking room where the building's primary network equipment, ISP demarcs, and core switches live.

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