# Multi-Repeater Network Coordination

When multiple MeshCore repeaters serve the same community, coordination between operators ensures the network behaves predictably and provides maximum benefit to users.

## Radio Preset Consistency (and the Channel-Key Myth)

A common misconception is that every repeater on a community network must share a "channel key." It does not. In MeshCore, **repeaters forward packets based on routing/path information and do not decrypt message payloads** — they relay encrypted traffic for any channel without needing that channel's key. Channel keys are a client-side concern: only clients holding a channel's key can read that channel's group messages. So a repeater never "silently drops traffic it cannot decrypt." What every repeater (and client) *must* share to interoperate is the same **radio preset / frequency** — if the radio parameters don't match, the repeater literally cannot hear the packets. When deploying a new repeater, coordinate the radio preset, frequency, and repeater naming/placement with the network coordinator before commissioning.

Verify a new repeater is relaying by sending a test message from a client node so that it routes through the new repeater. A successful delivery confirms the repeater is hearing and forwarding correctly (correct preset, placement, and RF range). It does *not* test channel-key alignment — that is verified between client nodes (whether two clients can read each other's group messages), not at the repeater. A failed route-through test points to a radio-config/preset mismatch or insufficient RF range, not a missing channel key.

## Coverage Overlap Planning

Adjacent repeaters should have some coverage overlap for redundancy and continuity. The exact amount depends on terrain, antenna height, and node density — there is no universal percentage. Validate overlap empirically with drive/walk tests confirming each area is reachable via at least two repeaters. Overlap provides:

- **Redundancy** - if one repeater goes offline, adjacent repeaters still serve the overlap area
- **Continuity of coverage for moving nodes** - when a mobile node leaves one repeater's range, its cached path will fail and MeshCore re-runs path discovery to find a route through the next in-range repeater. This is not a seamless cellular-style handoff — there is no association handed between repeaters; any in-range repeater simply relays. Expect a brief delivery gap while a new path is discovered. Overlap reduces, but does not eliminate, this gap.
- **Route diversity** - multiple path options between distant network segments improve end-to-end reliability

Insufficient overlap creates coverage holes where users are out of range of all repeaters. At the other extreme, deploying many repeaters very close together — covering the same footprint with no new coverage — adds channel airtime contention and flood amplification without proportional benefit. Note that close spacing is not inherently wasteful: in dense urban terrain with heavy building attenuation, sub-kilometer spacing can be necessary and appropriate (the density guidance suggests roughly one repeater per ~1 km² / ~500 m radius). Avoid overlap only where it is genuinely redundant.

## Frequency and Preset Coordination

All community repeaters must use the same radio parameters (the USA/Canada preset is recommended in this region). Verify with:

```
get radio
```

The `get radio` output shows the current frequency, bandwidth, spreading factor, and coding rate (`get freq` and `get tx` report frequency and TX power individually). MeshCore presets are an app-side selection; the serial CLI reports the raw radio parameters rather than a named preset. Confirm these values match the community-standard USA/Canada preset before committing a new repeater to service.

## Network Documentation

Maintain a community document with:

- Repeater name, operator callsign/contact
- Physical location (approximate - GPS coordinates if the operator consents to publishing)
- Power system type (mains, solar) and expected uptime
- Installation date and last maintenance date
- Known coverage limitations or issues

This documentation is invaluable when diagnosing network problems or planning expansion. Store it in a shared document that all operators can access and update.

## Repeater Retirement and Replacement

When a repeater is permanently taken offline, notify the community so they can update routing expectations and coverage maps. Removing a node that other nodes' cached routes depend on will cause temporary routing failures until routes are rediscovered. This is normal behavior; MeshCore re-discovers routes when existing paths fail.