7 min read · Published August 24, 2026 · Vast Networks
What actually takes fiber down
Excavation, overwhelmingly. Construction crews, utility work, agricultural equipment, and vehicles striking poles account for the majority of serious outages on terrestrial networks. Equipment failures and power problems happen too, but they are typically shorter and better protected against.
The relevant property of a cut is duration. Restoring a cut cable requires locating the break, mobilising a crew, exposing the cable, splicing each fiber, and testing. That is measured in hours, not minutes, which is why a single cut can exceed an annual availability allowance in one event.
The four ways apparent diversity fails
Shared underlying fiber: two providers selling you circuits may both lease capacity on the same physical cable. Different logos, one backhoe.
Shared building entrance: two circuits entering through the same conduit or the same riser fail together no matter how diverse the outside plant is.
Shared crossings: rivers, railways, and highways have limited crossing points, and routes that are genuinely separate for a hundred kilometres often converge at the only bridge.
Shared conduit segments: routes that diverge and then rejoin for a stretch, which is invisible from any order form and only appears in an actual route diversity review.
Degrees of diversity, and what each protects
Diverse building entrance means two physically separate entry points into your premises — this protects against the most localised and most common failure at the customer end. Diverse local access means separate paths from the building to the first aggregation point. Full route diversity means separate paths end to end between your two endpoints.
Each level costs more and protects against more. Being explicit about which you are buying prevents the common outcome where a customer believes they bought the third and actually bought the first.
How to verify rather than assume
Ask the provider to confirm diversity in writing, at the level you are buying. Ask specifically about the building entrance, about any shared conduit segments, and about crossings. If two providers are involved, ask each whether they lease capacity from the other or from a common third party — the answer is often yes and rarely volunteered.
Where diversity genuinely matters, some organizations commission a route diversity audit. It is not cheap and it is considerably cheaper than discovering the truth during an outage.
When diversity is not achievable
Sometimes only one physical route exists to a location, and no amount of budget changes that in a useful timeframe. The honest response is to say so and design around it: a connection on a different medium as failover, capacity to operate degraded, and a documented plan for a multi-hour outage.
A provider that promises diversity generically, before surveying the site, is describing an aspiration. It is a site-specific engineering question with a site-specific answer.