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ZigBee networks ZigBee router operation
XBee/XBee-PRO® S2C ZigBee® RF Module 63
route data packets and communicate with other devices on the network.
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:
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Has a valid 64-bit PAN ID (PAN ID matches ID if ID > 0)
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Has the correct stack profile ( ZS command)
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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.
Join a network
Once the router discovers a valid network, it sends an association request to the device that sent a
valid beacon requesting a join on the ZigBee network. The device allowing the join then sends an
association response frame that either allows or denies the join.
When a router joins a network, it receives a 16-bit address from the device that allowed the join. The
device that allowed the join randomly selects the 16-bit address.
Authentication
In a network where security is enabled, the router must follow an authentication process. See ZigBee
security for a discussion on security and authentication.
After the router is joined (and authenticated, in a secure network), it can allow new devices to join the
network.
Persistent data
Once a router joins a network, it retains the following information through power cycle or reset
events:
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PAN ID
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Operating channel
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Security policy and frame counter values
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Child table (end device children that are joined to the coordinator)