A lit building is one where a carrier's fiber already terminates inside, so it can deliver service over its own network with no construction; that is on-net. Off-net means the carrier leases the last mile from another network and takes over your traffic at an interconnection point, which usually adds cost, adds a second party to every repair, and can weaken the SLA or quietly remove path diversity. Neither is automatically wrong. You just need to know which one you are buying.
Our guide to why prices vary by building explains how lit, near-net and off-net status shape a quote. This article goes one level down: how an off-net circuit is actually put together, what that changes for you after installation, and how to check what you are getting before you sign. It applies to dedicated internet access most of all, because that is where buyers pay for an SLA and a clear path, but the same questions hold for any fiber circuit.
Why this matters more than it sounds
Buyers usually meet these terms as a line on a qualification report: lit, near-net, off-net. It is tempting to treat that line as a detail for the carrier to worry about. It is not. On-net status decides who owns the fiber in your riser, who shows up when it breaks, how quickly bandwidth can be raised, and whether the backup you pay for is really separate from the primary. Those are the things you feel on a bad day, long after the price has been forgotten.
The vocabulary, briefly
| Term | Meaning |
|---|---|
| Lit building | A building where a given carrier has active fiber terminated inside. "Lit" is always relative to a carrier. |
| On-net (sometimes called Type I) | Service delivered entirely over the selling carrier's own network, including the last mile. |
| Near-net | The carrier's fiber is close by but not in the building. A lateral would make it on-net. |
| Off-net (sometimes called Type II) | The selling carrier leases the last mile from another provider to reach you. |
| Last mile, or access | The connection between your building and the carrier's network. It may be far shorter than a mile. |
| NNI or ENNI | The network-to-network interface where the access provider hands your traffic to the selling carrier. |
| Demarcation point | Where the carrier's responsibility ends and yours begins inside the building. |
How an off-net circuit is built
Suppose Carrier A wins your order but has no fiber in your building. Carrier B does. Carrier A buys an access circuit from Carrier B, running from your building to a point where the two networks connect. At that NNI, your traffic passes onto Carrier A's network, and from there it is Carrier A's circuit.
From your side it looks like one service. You get one contract, one bill and one support number, all from Carrier A. The equipment in your telecom room, though, may belong to Carrier B, and so does the fiber up your riser and out to the street.
This is a normal, widely used arrangement. It is how carriers serve customers outside their own footprints, and it is how many multi-site companies get a single contract across locations. But it has consequences.
What changes for you
| On-net | Off-net | |
|---|---|---|
| Price | One carrier's cost | Selling carrier's price plus the cost of the leased access |
| Install | Often 2–4 weeks in a lit building | Depends on two carriers' order processes; can take longer |
| Repair | One network, one operations center | Your carrier must open a ticket with the access provider |
| SLA | Full carrier SLA | Sometimes the same, sometimes weaker; ask |
| Upgrades | Often a configuration change | May need the access provider to upgrade its part too |
| Path diversity | Known to the carrier | May share the access provider's path with other circuits |
Repair takes an extra step
When an off-net circuit fails, your carrier first works out whether the fault is on its network or on the access provider's. If it is on the access side, your carrier opens a ticket with that provider and waits for its technicians. You cannot usually call the access provider yourself, because you are not its customer. Most of the time this works well. When it does not, the delay tends to come from the handoff between two companies, not the repair itself.
The SLA may be different
Some carriers offer the same SLA on off-net circuits as on-net ones. Others apply a lower availability figure or a longer repair window, because part of the circuit is outside their control. Ask for the SLA that applies to your circuit type specifically, not the headline figure. For how SLAs work in general, see what a 99.99% SLA buys.
The diversity trap
This is the one that catches people. Suppose your primary circuit is on-net with Carrier B. For resilience, you buy a backup from Carrier A, a completely different company. But Carrier A is off-net in your building and leases its last mile from Carrier B. Your two circuits now run through the same equipment, the same riser and the same conduit to the street. A single cut takes out both, and you have paid for two carriers to get one path.
It is easy to avoid if you ask. For any backup circuit, find out whether it is on-net and, if not, who provides the access. If the answer is the same network as your primary, choose a different backup: a carrier that is on-net on a different entrance, coax from a cable network, or fixed wireless. We cover backup design in more depth in does your business need backup internet.
"Lit" is not the whole answer
Even on-net, a few details can surprise you.
- Lit in the building, not on your floor. The carrier's fiber may end in the basement. Getting service to your suite may need a riser extension, which takes time and sometimes costs extra.
- Lit, but full. Occasionally the carrier's equipment in the building has no spare capacity, and it needs an upgrade before it can take your order.
- Lit lists go out of date. A carrier's database may list a building that was served by a tenant who left, or miss one that was recently built. Qualification should confirm with the carrier for your exact address.
When off-net is perfectly fine
- Small sites where the price difference matters more than repair handling.
- Branch offices in markets where your main carrier has no network of its own, and one contract across all sites is worth the trade.
- Private links between sites, such as Ethernet transport, where one carrier stitches together access from several networks so you do not have to manage them.
- The only option. If no carrier is lit and construction does not make sense, an off-net circuit can be better than waiting.
A worked example
Hypothetical illustration. The carriers, building and figures are invented to show the mechanism.
A clinic runs its primary circuit on-net with Carrier B. Wanting a backup, it asks two carriers for quotes. Carrier A offers a backup circuit that is $100 a month cheaper than Carrier C's. Asked the right question, Carrier A confirms it is off-net and uses Carrier B for access. Carrier C is on-net in the building, using a separate entrance on the opposite side.
The cheaper backup would have saved $1,200 a year and protected the clinic from almost nothing that matters, because a cut in Carrier B's conduit would take out both circuits together. Carrier C's backup costs more but fails for different reasons. Alternatively, a coax circuit from a cable network might offer the same diversity for less. The clinic chooses between C and coax, and rules out A. The saving on A was real, but the backup would not have done its job.
What status does to your next renewal
On-net status also changes your position later on. A carrier that is lit in your building can usually re-price or upgrade your circuit without anyone else involved, and it knows other lit carriers can take the order. An off-net circuit carries the access provider's cost inside it, which puts a floor under what your carrier can offer. At renewal, it is worth checking whether any carrier has since become lit in your building, because an off-net circuit that was the best option three years ago may not be today.
How to check what you are getting
- Ask in writing whether the circuit will be on-net or off-net at your exact address.
- If off-net, ask who provides the access and where the handoff happens.
- Ask which building entrance and riser the circuit will use.
- Compare against your other circuits, to spot shared paths.
- After install, look at the equipment. Labels on the device in your telecom room often show which network it belongs to.
Status also affects scheduling, as our guide to fiber installation timelines explains.
Questions to ask your carrier
- Is this circuit on-net or off-net at my address?
- If off-net, which network provides the last mile, and where is the handoff?
- Does the same SLA apply to off-net circuits, including repair time?
- Who dispatches the technician if the fault is on the access side?
- If I upgrade later, does the access provider have to upgrade its part too?
- Does this circuit share an entrance, riser or conduit with my existing service?
Know what is under the brand name
When we qualify your address, we ask every carrier whether it is on-net, off-net or near-net, and who provides the access where it matters. You see that next to the price, so a cheaper circuit that shares a path with your primary does not slip through. Tier 1 carriers bid, the carrier pays us, and your invoice is never marked up. See the service areas page for the markets we cover, then send us your address, call 478-758-8091 or text (347) 870-0965. The quote is free with no obligation, and we usually respond the same day.
