Error seen when connecting to switch as not able to detect a prompt

[pnikila]

Description of Issue/Question

1. I am connecting to cisco switch via console port.
2. I am getting the below error :

An Error Occured:
Pattern not detected: '' in output.

Things you might try to fix this:

1. Explicitly set your pattern using the expect_string argument.
2. Increase the read_timeout to a larger value.

You can also look at the Netmiko session_log or debug log for more information.

An Error Occured: 'NoneType' object has no attribute 'write_channel'

3. When manually try to connect to the switch, we have to press "Enter Key" and then console prompt comes.
4. Now, when I again try to connect to the switch, I am able to connect to the switch.
5. So, is there any way that when connecting to switch, netmiko gives "Enter" to detect prompt for connecting to device.

Setup

device_dict_cisco_serial = {
"device_type" : "terminal_server",
"ip":device_dict_cisco["serial_ip"],
"port":device_dict_cisco["serial_port"],
"username":device_dict_cisco["serial_username"],
"password":device_dict_cisco["serial_password"],
"global_delay_factor": 2,
"session_log":device_dict_cisco["session_log"],
"secret":device_dict_cisco["secret"],
"fast_cli":False
}
netmiko_dev = ConnectHandler(**device_dict_cisco_serial)
netmiko_dev.send_command('\n\n')
netmiko.redispatch(netmiko_dev, device_type=device_dict_cisco["device_type"])
return netmiko_dev

Netmiko version

(Paste verbatim output from pip freeze | grep netmiko between quotes below)

netmiko            4.4.0

Netmiko device_type (if relevant to the issue)

(Paste device_type between quotes below)

cisco_ios

Steps to Reproduce the Issue

1)Connect to serial console

Error Traceback

(Paste the complete traceback of the exception between quotes below)

An Error Occured:
Pattern not detected: '' in output.

Things you might try to fix this:
1. Explicitly set your pattern using the expect_string argument.
2. Increase the read_timeout to a larger value.

You can also look at the Netmiko session_log or debug log for more information.



An Error Occured: 'NoneType' object has no attribute 'write_channel'

Relevant Python code

(Please try to essentialize your Python code to the minimum code needed to reproduce the issue)
(Paste the code between the quotes below)

device_dict_cisco_serial = {
           "device_type" : "terminal_server",
                "ip":device_dict_cisco["serial_ip"],
                "port":device_dict_cisco["serial_port"],
                "username":device_dict_cisco["serial_username"],
                "password":device_dict_cisco["serial_password"],
                "global_delay_factor": 2,
                "session_log":device_dict_cisco["session_log"],
                "secret":device_dict_cisco["secret"],
                "fast_cli":False
            }
            netmiko_dev = ConnectHandler(**device_dict_cisco_serial)
            netmiko_dev.send_command('\n\n')
            netmiko.redispatch(netmiko_dev, device_type=device_dict_cisco["device_type"])

[ktbyers]

Can you post the full exception stack trace (i.e. all the line numbers where the error occurred)? This let's me see where the error is occuring.

[pnikila]

Traceback (most recent call last):

netmiko_dev.send_command('\n\n')

File "D:......\myvenv\Lib\site-packages\netmiko\base_connection.py", line 111, in wrapper_decorator

return_val = func(self, *args, **kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^

File "D:....\myvenv\Lib\site-packages\netmiko\utilities.py", line 596, in wrapper_decorator
return func(self, *args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "D:.....\myvenv\Lib\site-packages\netmiko\base_connection.py", line 1764, in send_command
search_pattern = self._prompt_handler(auto_find_prompt)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "D:....\myvenv\Lib\site-packages\netmiko\base_connection.py", line 1643, in _prompt_handler
prompt = self.find_prompt()
^^^^^^^^^^^^^^^^^^
File "D:.....\myvenv\Lib\site-packages\netmiko\base_connection.py", line 1439, in find_prompt
time.sleep(sleep_time)
KeyboardInterrupt

[pnikila]

After removing the line netmiko_dev.send_command('\n\n') from code, we get this below error :

An Error Occured:

Pattern not detected: 'terminal width 511' in output.

Things you might try to fix this:

1. Adjust the regex pattern to better identify the terminating string. Note, in
   many situations the pattern is automatically based on the network device's prompt.
2. Increase the read_timeout to a larger value.

You can also look at the Netmiko session_log or debug log for more information.

An Error Occured: 'NoneType' object has no attribute 'write_channel'

In Netmiko log only this is present:
exit

[pnikila]

Hi,
By using a loop to write_channel and read_channel , I am able to resolve this issue and connect to the device.
netmiko_dev.write_channel('\r')
time.sleep(1)
output = netmiko_dev.read_channel()