As an example, I will reset the settings on the BDCOM GP3600-08B, on other models the procedure is similar.
Connect the console cable to the turned off device, open the terminal, turn on the power, immediately hold down the Ctrl+P keys, hold them and wait for monitor# to appear, if you press the keys late, the device can start to boot in normal mode, in this case, start over.
Now delete the configuration in the device and the interface index file:
delete startup-config
delete config.db
delete ifindex-config
By the way, these commands can also be executed when connecting to the device via telnet and in normal mode through the console.
Let’s reboot the device:
reboot
See also my articles:
Configuring BDCOM GP3600
BDCOM P3310 Reset Configuration