# Building a Community Mesh-Network ISP

Our neighborhood mesh network began with a practical problem: several streets had unreliable broadband, while a nearby apartment building had affordable fiber service. Instead of waiting for another provider, residents formed a cooperative ISP. The cooperative leases a business fiber circuit, operates the gateway and routing infrastructure, and distributes connectivity through rooftop wireless links. Members pay monthly dues that cover transit, equipment replacement, insurance, and a small reserve for expansion.

## Network Architecture

The network uses a hybrid topology rather than a pure consumer-style mesh. Stable rooftops and community buildings form the backbone with directional 5 GHz and 60 GHz point-to-point links. Smaller relay nodes connect to at least two backbone sites when possible, while subscriber radios attach to the nearest suitable relay. This design preserves redundant paths without forcing every packet through several low-capacity radios.

Each router runs an interior routing protocol that measures link quality and automatically selects viable paths. Subscriber traffic is carried in separate VLANs to prevent members from accessing one another's devices, and IPv6 prefixes are delegated directly to homes. IPv4 uses carrier-grade NAT because obtaining portable address space remains expensive for a small cooperative.

```ini
# Example Babel interface configuration
[interface "mesh0"]
type = "tunnel"
rxcost = 96
hello-interval = 4
enable-timestamps = true
```

## Operations and Reliability

Monitoring is as important as radio placement. Every backbone node reports latency, packet loss, signal strength, temperature, and available battery runtime to a central dashboard. Alerts go to an on-call rotation of trained volunteers, but configuration changes require review by a second operator. Nodes keep their last known-good configuration locally, allowing them to continue routing during a management-server outage.

## Capacity, Policy, and Growth

The cooperative publishes expected speeds instead of advertising an unrealistic maximum. During busy hours, fair-queueing limits the impact of large downloads and keeps video calls responsive. New installations require a line-of-sight survey, documented mounting approval, and enough projected capacity on the upstream path. That discipline makes growth slower, but it prevents a popular relay from quietly becoming the bottleneck for an entire block.

## Lessons Learned

The hardest parts were organizational rather than technical: negotiating rooftop access, documenting maintenance responsibilities, and ensuring that knowledge did not remain with one volunteer. Clear governance, standardized hardware, spare radios, and written recovery procedures turned an experimental mesh into a credible local ISP. The result is not free internet; it is community-owned infrastructure whose costs, limitations, and priorities are visible to the people who depend on it.