Comtrol DeviceMaster LT User Manual page 114

General Troubleshooting
114 - Troubleshooting and Technical Support
General Condition
DeviceMaster LT
continuously reboots
when connected to some
Ethernet switches with
the NS-Link driver
DeviceMaster LT
continuously reboots
when connected to some
Ethernet switches or
routers
Explanation/Action
The problem is caused by a L2 bridging feature called
Spanning Tree Algorithm (STA) in the switch. This
feature is enabled by default in some switches. This
features causes time-out problems on certain L2
protocols, such as our MAC mode.
Resolution: There will be no firmware fix for this
problem. Only one of the following fixes is required for
resolution.
1. Disable STA in the switch.
2. Enable STA fast forwarding on the port.
3. Change the STA Forward Delay and Message Age to
minimum time values.
4. On the device, set the time-out value to 0 (to disable
loading of SocketServer) or 120. The command from
the redboot prompt is "Timeout 120" without the
quotes.
Problem Details: STA by default blocks packets for 30
seconds after an ethernet port auto negotiates. Blocking
of these packets causes the NS-Link driver load process
to fail.
The normal NS-Link driver load process is:
1. If NS-Link determines that it needs to load a device,
it resets the device. It does this to get the device into
RedBoot mode. Only RedBoot accepts load binary
commands, which are needed to load the NS-Link
binary into the DeviceMaster LT.
2. After a 6 second delay, NS-Link sends an ID query
to the device. This query is to verify that the device
is in RedBoot and can accept load binary commands.
3. The device sends an ID query response.
4. NS-Link loads the device.
If the device is not loaded after timeout seconds (default
15), it loads SocketServer.
The above process fails when STA is running because
the switch blocks packets for 30 seconds after the
DeviceMaster LT reboots. Therefore, the ID query is not
received by the DeviceMaster LT and after 15 seconds
the device loads SocketServer. After 30 seconds, NS-
Link finally can do an ID query, which reveals that the
device is not in RedBoot. NS-Link therefore reboots the
device, and the process repeats.
Invalid IP information may also cause the switch or
router to check for a gateway address. Lack of a
gateway address is a common cause.
DeviceMaster LT User Guide: 2000586 Rev. B