red lion BT-6821-AT-AC User Manual page 61

Troubleshooting
The modem must be configured to forward incoming traffic to the device, otherwise your connection attempts will
never reach the device. Refer to IP Networking Features for further details.
12.3.3 (SERIAL) You cannot communicate with a device behind the modem
First, make sure the modem is configured to enable outside communication with the attached device. Refer to the
"Serial IP" section of the main guide for details. The troubleshooting steps below assume the modem is configured
properly.
Possible cause #1
The modem and the device are using different serial port settings.
Troubleshooting
Using BlueVue Device Manager, navigate to CONF (Modem Configuration) > Serial Port, and change the serial port
settings to the same values as those of the serial device. If the CTS and RTS pins are partially (or both) disabled, set the
modem to use no flow control ("none").
Possible cause #2
The cable wiring is incorrect.
Troubleshooting
Refer to Section 11.6 for details on the required cable type.
Possible cause #3
The DTR signal is inconsistent.
Troubleshooting
A flickering DTR signal will interrupt communication with the modem. The modem can be configured to ignore the
changes in the DTR state. In BlueVue Device Manager, navigate to CONF (Modem Configuration) > Serial Port, and
check the option to Ignore DTR.