# LAN Graph Explorer

A local LAN discovery service that pings every host on your primary subnet, optionally uses SSH key-based auth to query remote neighbors, and presents a Visio-style map via D3.

## Features
- Detects your default IPv4 network and gateway automatically.
- Pings each active host and performs reverse DNS lookup.
- Attempts passwordless SSH (honoring `SSH_USER`/`SSH_KEY_PATH`) to collect `ip neigh` data so we can draw edges between hosts.
- Serves a FastAPI backend and a D3-powered front-end that renders nodes/edges interactively.

## Getting started
1. Install dependencies (ideally inside a virtualenv):
   ```bash
   pip install --upgrade pip
   pip install fastapi uvicorn[standard] typer
   ```
2. Run a scan from the command line:
   ```bash
   lan-graph scan --concurrency 64 --ssh-timeout 5
   ```
3. Start the UI server:
   ```bash
   lan-graph serve --host 0.0.0.0 --port 8000
   ```
   Open `http://localhost:8000` in a browser to see the topology.

## SSH key authentication
Set environment variables so the scanner uses your preferred SSH identity:
```bash
export SSH_USER=team
export SSH_KEY_PATH=~/.ssh/id_rsa
```
The tool runs `ssh -o BatchMode=yes` and will skip hosts where it cannot connect quickly.

## Testing
```bash
pip install pytest
pytest
```

## Notes
- The graph draws gateways, the scanning host, and any discovered neighbor relationships for hosts that allow `ssh`.
- It's designed to run on Linux machines with `ip`, `ping`, and `ssh` in place.