Comtrol DeviceMaster PRO Installation And Configuration Manual page 100

General Troubleshooting
100 - Troubleshooting and Technical Support
General Condition
DeviceMaster
continuously reboots
when connected to some
Ethernet switches
DeviceMaster
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 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 device.
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
is rebooted. Therefore, the ID query is not received by the
DeviceMaster 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 Installation and Configuration Guide: 2000506 Rev. B