# Building a Community Mesh-Network ISP

In Northbridge, unreliable broadband and high installation costs led residents to build a cooperative wireless ISP. The network began with three rooftop sites connected to a donated fiber circuit and now serves roughly 180 homes. Members pay a modest monthly fee that covers transit, equipment replacement, insurance, and tower leases; major changes are approved through quarterly community meetings.

## Network Architecture

Each rooftop site uses a sector antenna for subscriber access and dedicated 60 GHz radios for backhaul. Where buildings lack clear line of sight, 5 GHz links form a self-healing mesh using Babel, a routing protocol designed for dynamic networks. Two gateway sites advertise default routes, while internal prefixes remain reachable if either gateway or an intermediate relay fails.

Customer routers receive addresses through DHCP, but infrastructure links use static IPv6 assignments from the cooperative’s delegated prefix. Traffic is separated into management, subscriber, and public-service VLANs. This prevents a compromised household device from reaching radio administration interfaces while allowing community resources—such as the library mirror and local VoIP server—to remain accessible during an upstream outage.

```conf
# Example Babel interface configuration
interface mesh0 type tunnel
interface mesh0 rxcost 96
redistribute ip 10.42.0.0/16 allow
redistribute local deny
```

## Operating the Network

Volunteer operators monitor packet loss, signal-to-noise ratio, route changes, and gateway utilization with Prometheus and Grafana. Alerts target sustained conditions rather than brief spikes, because rain, construction equipment, and seasonal tree growth can temporarily affect wireless paths. Firmware upgrades are staged on a test link, deployed to one production site, and then rolled out network-wide after 48 hours without regressions.

## Lessons from the Field

The hardest problems have been organizational rather than technical. Rooftop access agreements, documented maintenance procedures, spare-part inventory, and a clear escalation rota matter as much as radio selection. The cooperative also publishes expected speeds and outage reports, which helps members understand that a community ISP is shared infrastructure—not a commercial service with invisible operations—and gives them a practical role in improving it.