# Building a Community Mesh-Network ISP

When our neighborhood’s only broadband provider raised prices again, a group of residents formed a cooperative ISP. The initial network connected 38 homes using rooftop radios, with a leased fiber circuit at the local library serving as the upstream connection. Each member contributed toward equipment and paid a monthly fee covering transit, hosting, maintenance, and a small replacement reserve.

## Network Architecture

The access layer uses directional 5 GHz links between rooftops, while a few taller buildings act as distribution sites with sector antennas. Most homes have at least two possible paths to a gateway, allowing traffic to reroute when a radio fails or trees obstruct a link. We use Babel for route selection because it handles changing wireless link quality more gracefully than shortest-path routing alone.

Each distribution router runs Linux and advertises measured prefixes through the mesh. A simplified Babel configuration looks like this:

```conf
interface wlan-mesh
interface backbone
redistribute ip 10.42.0.0/16
redistribute local deny
```

## Operating Like an ISP

The difficult work is less about radios than operations. We monitor packet loss, signal-to-noise ratio, airtime utilization, and gateway capacity, then alert volunteers only when thresholds remain unhealthy for several minutes. Subscriber traffic is rate-limited per household, but local traffic—such as backups to the cooperative’s storage server—does not consume upstream bandwidth.

## Reliability and Security

Power failures remain the most common source of outages, so core sites use small UPS units and automatically restart after extended interruptions. Management services are isolated from subscriber networks, configuration access requires WireGuard and hardware-backed SSH keys, and firmware updates are tested on spare equipment before deployment. We also publish maintenance notices and aggregate availability statistics so members can see how the network is performing.

## Lessons From the First Year

After twelve months, the mesh serves 112 households and typically delivers 80–150 Mbps per home. Dense clusters perform well, while long rural links require careful alignment and occasional relay sites. The cooperative’s biggest advantage is not unlimited bandwidth; it is local accountability, shared infrastructure, and a network that can evolve around the community’s actual needs.