> ## Documentation Index
> Fetch the complete documentation index at: https://docs.hologram.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Troubleshooting device tunneling

> Resolve common Spacebridge tunneling issues and key limitations.

Spacebridge enables secure SSH tunnels to devices on the Hologram network.

## Troubleshooting Spacebridge

1. Ensure SSH is running on the target device.
2. Ensure the cellular interface is the default route.
3. Confirm the device is connected and passing data on the cellular interface.
4. Verify responses are not routed over Wi-Fi or Ethernet instead of the cellular link.

## "You are only allowed 5 tunnel keys" error

Hologram issues each user a maximum of 5 tunnel keys. You can enable/disable keys via the REST API.

<Note>
  **Note:** Tunnel keys are mapped to desktop clients (computers), not SIMs/devices.
</Note>

## Related actions

<Card title="Enable/disable tunneling keys via API" href="/guides/communication/enable-and-disable-device-tunneling-keys-using-the-rest-api" horizontal />

<Card title="View tunneling keys via API" href="/guides/communication/view-device-tunneling-keys-using-the-rest-api" horizontal />