Creating an ASCII art diagram for your VXLAN example with three sites can help visualize the network setup in a simple and effective way. Here's an ASCII representation that outlines the multi-site deployment, including OPNsense gateways, Debian devices configured with VXLAN, and connections managed through dynamic DNS.

```
 +----------------+       +----------------+       +----------------+
 |                |       |                |       |                |
 |   Site A       |       |   Site B       |       |   Site C       |
 |                |       |                |       |                |
 | OPNsense A     |       | OPNsense B     |       | OPNsense C     |
 | 192.168.10.1   |       | 192.168.20.1   |       | 192.168.30.1   |
 +-------+--------+       +-------+--------+       +-------+--------+
         |                        |                        |
         |                        |                        |
         |                        |                        |
         v                        v                        v
 +-------+--------+       +-------+--------+       +-------+--------+
 |                |       |                |       |                |
 | Debian A       |       | Debian B       |       | Debian C       |
 | 10.0.0.1       |<----->| 10.0.0.2       |<----->| 10.0.0.3       |
 | VXLAN ID 100   |       | VXLAN ID 100   |       | VXLAN ID 100   |
 +----------------+       +----------------+       +----------------+
```

### Explanation of the ASCII Diagram:
- **OPNsense Gateways**: Each site has an OPNsense gateway configured with an internal IP address.
- **Arrows**: The arrows (`<----->`) represent the VXLAN tunnels between Debian devices. These arrows indicate bidirectional traffic flow, essential for illustrating that each site can communicate with the others via the VXLAN overlay.
- **Debian Devices**: These are set up with VXLAN. Each device is assigned a unique local IP but shares a common VXLAN ID, which is crucial for establishing the VXLAN network across all sites.
- **IP Addresses**: Simplified IP addresses are shown for clarity. In a real-world scenario, these would need to be public IPs or routed properly through NAT configurations.

This ASCII diagram provides a clear, simple view of how each component is interconnected in your VXLAN setup, suitable for inclusion in Markdown documentation, presentations, or network planning documents. It’s a useful tool for both explaining and planning network configurations.