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Nokia SR OS/Alcatel AOS - randomly returned ValueError: router prompt not found

See original GitHub issue

I have a problem with randomly returned ValueError and router prompt not found message for Alcatel/Nokia devices. Error occurs totally randomly. When I’m running my script once again after error occurs everything goes fine.

Part of my connection settings (I noticed that the only changes I made before the problem started was increasing the following parameters value):

 connection_credentials = {
           [...]
           "banner_timeout": 60,
           "timeout": 300,
           "session_timeout": 180
}

Stack trace:

[...]
  File "/path/to/file/file.py", line 54, in connect_to_host
    self.connection = ConnectHandler(**connection_credentials)
  File "/usr/local/lib/python3.6/site-packages/netmiko/ssh_dispatcher.py", line 259, in ConnectHandler
    return ConnectionClass(*args, **kwargs)
  File "/usr/local/lib/python3.6/site-packages/netmiko/base_connection.py", line 327, in __init__
    self._open()
  File "/usr/local/lib/python3.6/site-packages/netmiko/base_connection.py", line 333, in _open
    self._try_session_preparation()
  File "/usr/local/lib/python3.6/site-packages/netmiko/base_connection.py", line 756, in _try_session_preparation
    self.session_preparation()
  File "/usr/local/lib/python3.6/site-packages/netmiko/nokia/nokia_sros_ssh.py", line 38, in session_preparation
    self.set_base_prompt()
  File "/usr/local/lib/python3.6/site-packages/netmiko/nokia/nokia_sros_ssh.py", line 52, in set_base_prompt
    cur_base_prompt = super().set_base_prompt(*args, **kwargs)
  File "/usr/local/lib/python3.6/site-packages/netmiko/base_connection.py", line 1081, in set_base_prompt
    raise ValueError(f"Router prompt not found: {repr(prompt)}")
ValueError: Router prompt not found: 'A:'

Logs when the problem doesn’t occur:

09/17/2020 09:30:38:DEBUG:paramiko.transport:userauth is OK
09/17/2020 09:30:38:INFO:paramiko.transport:Authentication (password) successful!
09/17/2020 09:30:38:DEBUG:paramiko.transport:[chan 0] Max packet in: 32768 bytes
09/17/2020 09:30:38:DEBUG:paramiko.transport:[chan 0] Max packet out: 32768 bytes
09/17/2020 09:30:38:DEBUG:paramiko.transport:Secsh channel 0 opened.
09/17/2020 09:30:38:DEBUG:paramiko.transport:[chan 0] Sesch channel 0 request ok
09/17/2020 09:30:38:DEBUG:paramiko.transport:[chan 0] Sesch channel 0 request ok
09/17/2020 09:30:39:DEBUG:netmiko:read_channel: ^M
^M
A:HOST1#
09/17/2020 09:30:39:DEBUG:netmiko:read_channel:
09/17/2020 09:30:41:DEBUG:netmiko:read_channel:
09/17/2020 09:30:41:DEBUG:netmiko:read_channel:
09/17/2020 09:30:41:DEBUG:netmiko:write_channel: b'\n'
09/17/2020 09:30:41:DEBUG:netmiko:read_channel: ^M
A:HOST1#
09/17/2020 09:30:41:DEBUG:netmiko:read_channel:
09/17/2020 09:30:41:DEBUG:netmiko:[find_prompt()]: prompt is A:HOST1#
09/17/2020 09:30:42:DEBUG:netmiko:read_channel:
09/17/2020 09:30:42:DEBUG:netmiko:In disable_paging
09/17/2020 09:30:42:DEBUG:netmiko:Command: environment no more

Logs when the problem occurs:

09/17/2020 09:42:16:DEBUG:paramiko.transport:userauth is OK
09/17/2020 09:42:17:INFO:paramiko.transport:Authentication (password) successful!
09/17/2020 09:42:17:DEBUG:paramiko.transport:[chan 0] Max packet in: 32768 bytes
09/17/2020 09:42:17:DEBUG:paramiko.transport:[chan 0] Max packet out: 32768 bytes
09/17/2020 09:42:17:DEBUG:paramiko.transport:Secsh channel 0 opened.
09/17/2020 09:42:17:DEBUG:paramiko.transport:[chan 0] Sesch channel 0 request ok
09/17/2020 09:42:17:DEBUG:paramiko.transport:[chan 0] Sesch channel 0 request ok
09/17/2020 09:42:18:DEBUG:netmiko:read_channel:

A:HOST2#
09/17/2020 09:42:18:DEBUG:netmiko:read_channel:
09/17/2020 09:42:20:DEBUG:netmiko:read_channel:
09/17/2020 09:42:20:DEBUG:netmiko:read_channel:
09/17/2020 09:42:20:DEBUG:netmiko:write_channel: b'\n'
09/17/2020 09:42:20:DEBUG:netmiko:read_channel:
A:
09/17/2020 09:42:20:DEBUG:netmiko:read_channel: HOST2#
09/17/2020 09:42:20:DEBUG:netmiko:Clear buffer detects data in the channel
09/17/2020 09:42:21:DEBUG:netmiko:read_channel:
09/17/2020 09:42:21:DEBUG:netmiko:[find_prompt()]: prompt is A:
09/17/2020 09:42:21:DEBUG:netmiko:write_channel: b'logout\n'
09/17/2020 09:42:21:DEBUG:paramiko.transport:EOF in transport thread

Issue Analytics

State:
Created 3 years ago
Comments:7 (3 by maintainers)

Top GitHub Comments

2reactions

ktbyerscommented, Oct 6, 2020

Adding @hellt also.

I will probably look at this, but it might be next week. Not sure I am going to get to it this week.

0reactions

ktbyerscommented, Oct 6, 2020

Okay, it seems like the generally issue is that in some situations find_prompt() is failing to get the last character i.e. the # and that is causing problems.

I will have to look into why that is happening.

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