User Manual

XBee®/XBee‐PRO®ZBRFModules
©2011DigiInternational,Inc. 75
Updating the Network Key with a Trust Center
If the trust center has started a network and the NK value is changed, the coordinator will update the
network key on all devices in the network. (Changes to NK will not force the device to leave the network.)
The network will continue to operate on the same channel and PAN ID, but the devices in the network will
update their network key, increment their network key sequence number, and restore their frame counters
to 0.
Updating the Network Key without a Trust Center
If the coordinator is not running as a trust center, the network reset command (NR1) can be used to force
all devices in the network to leave the current network and rejoin the network on another channel. When
devices leave and reform then network, the frame counters are reset to 0. This approach will cause the
coordinator to form a new network that the remaining devices should join. Resetting the network in this
manner will bring the coordinator and routers in the network down for about 10 seconds, and will likely
cause the 16-bit PAN ID and 16-bit addresses of the devices to change.
XBee Security Examples
This section covers some sample XBee configurations to support different security modes. Several AT commands are
listed with suggested parameter values. The notation in this section includes an '=' sign to indicate what each
command register should be set to - for example, EE=1. This is not the correct notation for setting command values
in the XBee. In AT command mode, each command is issued with a leading 'AT' and no '=' sign - for example ATEE1.
In the API, the two byte command is used in the command field, and parameters are populated as binary values in
the parameter field.
Example 1: Forming a network with security (pre-configured link keys)
1. Start a coordinator with the following settings:
a. ID=2234 (arbitrarily selected)
b. EE=1
c. NK=0
d. KY=4455
e. WR (save networking parameters to preserve them through power cycle)
2. Configure one or more routers or end devices with the following settings:
a. ID=2234
b. EE=1
c. KY=4455
d. WR (save networking parameters to preserve them through power cycle)
3. Read the AI setting on the coordinator and joining devices until they return 0 (formed or joined 
a network).
In this example, EE, ID, and KY are set the same on all devices. After successfully joining the secure network,
all application data transmissions will be encrypted by the network key. Since NK was set to 0 on the
coordinator, a random network key was selected. And since the link key (KY) was configured the same on all
devices, to a non-zero value, the network key was sent encrypted by the pre-configured link key (KY) when the
devices joined.
Example 2: Forming a network with security (obtaining keys during joining)
1. Start a coordinator with the following settings:
a. ID=2235
b. EE=1
c. NK=0
d. KY=0