# Building a Community Mesh-Network ISP

Our neighborhood mesh began with six rooftops, a shared fiber connection, and a practical goal: provide reliable internet where commercial service was slow or unaffordable. Each member hosts an outdoor wireless node that connects to at least two nearby nodes. Traffic travels across these links until it reaches one of several gateway sites, where it exits through wholesale transit purchased by the cooperative.

## Network Architecture

The backbone uses directional 5 GHz and 60 GHz radios between rooftops, while local subscribers connect through conventional indoor Wi-Fi access points. Nodes run Linux and exchange routes using Babel, which reacts quickly when rain, construction, or a powered-off site changes link quality. We assign IPv6 prefixes directly to households and use carrier-grade NAT for legacy IPv4 traffic.

```ini
# /etc/babeld.conf
interface mesh0 type wireless
interface mesh1 type wireless
redistribute ip 2001:db8:4200::/48
redistribute local deny
```

## Operations and Reliability

Two gateway sites terminate independent upstream connections, and policy routing distributes normal traffic between them. If either gateway fails, Babel withdraws its default route and subscribers automatically use the remaining path. Prometheus collects radio signal, packet-loss, and battery-voltage metrics, while alerts distinguish a failed node from a link that is merely congested.

## Capacity Planning

Mesh networks can fail gradually rather than dramatically: every subscriber remains connected, but shared relay links become saturated during evening peaks. We therefore measure airtime utilization as well as throughput, reserve backbone channels that are separate from household Wi-Fi, and add wired or fiber-fed gateways before heavily relayed areas exceed 60 percent sustained utilization.

## Governance and Lessons Learned

The hardest problems have been organizational rather than wireless. Members approve pricing, privacy rules, and equipment budgets at monthly meetings, while trained volunteers handle installations under documented safety procedures. Clear service expectations matter: the cooperative offers best-effort residential access, publishes outage reports, and keeps enough subscription revenue in reserve to replace critical radios without waiting for a fundraiser.