Discover Zigbee networks

To discover nearby Zigbee networks, the router performs a PAN (or active) scan, just like the coordinator does when it starts a network. During the PAN scan, the router sends a beacon request (broadcast) transmission on the first channel in its scan channels list. All nearby coordinators and routers operating on that channel that are already part of a Zigbee network respond to the beacon request by sending a beacon back to the router.

The beacon contains information about the PAN the nearby device is on, including the PAN identifier (PAN ID), and whether or not joining is allowed. The router evaluates each beacon received on the channel to determine if it finds a valid PAN. A PAN is valid if any of the following exist:

• Has a valid 64-bit PAN ID (PAN ID matches ID if ID > 0)
• Has the correct stack profile (ZS command)
• Allows joining the network

If the router does not find a valid PAN, it performs the PAN scan on the next channel in its scan channels list and continues scanning until it finds a valid network, or until all channels have been scanned. If the rounter scans all channels and does not discover a valid PAN, it scans all channels again.

The Zigbee Alliance requires that certified solutions not send beacon request messages too frequently. To meet certification requirements, the XBee firmware attempts nine scans per minute for the first five minutes, and three scans per minute thereafter. If a valid PAN is within range of a joining router, it typically discovers the PAN within a few seconds.