Netmiko - 如何保持或断开 telnet 连接？答案

【问题标题】：Netmiko - How to hold or disconnect a telnet connection?Netmiko - 如何保持或断开 telnet 连接？
【发布时间】：2022-05-24 02:24:43
【问题描述】：

问题

如何保持或断开 telnet 连接而不会出错？

情况

我想用Nornir重新加载路由器，但是触发时终端会显示错误信息EOFError: telnet connection closed。

行动

我尝试在重新加载 telnet 连接后使用r1.close_connections()，但它仍然触发了之前的EOFError。

当reloading命令被触发时，路由器必须重启系统，所以telnet会话会被断开。

环境

Python 3.9.6
nornir==3.1.1
nornir-jinja2==0.2.0
nornir-napalm==0.1.2
nornir-netmiko==0.1.1
nornir-rich==0.1.2
nornir-utils==0.1.2
netmiko==3.4.0
nornir-netmiko==0.1.1

预期结果

重新加载路由器。
- 当reloading命令被触发时，路由器必须重启系统，所以telnet会话会被断开。
等待路由器重新加载时间。

显示路由器版本。

执行代码

from time import sleep
from nornir import InitNornir
from nornir_netmiko import netmiko_send_command as send_cmd, netmiko_send_config


def reboot_device(task):
    task.run(
        task=netmiko_send_command,
        use_timing=True,
        command_string=\"reload\",
    )
    task.run(
        task=netmiko_send_command,
        use_timing=True,
        command_string=\'y\',
    )


def main():
    nr = InitNornir(config_file=\"config.yaml\")
    r1 = nr.filter(device_name=\"R1\")
    reload_time = 60

    r1.run(task=reboot_device)
    sleep(reload_time)
    r1.run(
        task=netmiko_send_command,
        use_timing=True,
        command_string=\"show version\"
    )


if __name__ == \"__main__\":
    main()

错误信息

2022-05-21 18:35:34,126 - nornir.core.task -    ERROR -      start() - Host \'R1\': task \'netmiko_send_command\' failed with traceback:
Traceback (most recent call last):
  File \"/usr/local/lib/python3.9/site-packages/nornir/core/task.py\", line 99, in start
    r = self.task(self, **self.params)
  File \"/usr/local/lib/python3.9/site-packages/nornir_netmiko/tasks/netmiko_send_command.py\", line 30, in netmiko_send_command
    result = net_connect.send_command_timing(command_string, **kwargs)
  File \"/usr/local/lib/python3.9/site-packages/netmiko/utilities.py\", line 500, in wrapper_decorator
    return func(self, *args, **kwargs)
  File \"/usr/local/lib/python3.9/site-packages/netmiko/base_connection.py\", line 1303, in send_command_timing
    new_data = self.read_until_pattern(pattern=re.escape(cmd))
  File \"/usr/local/lib/python3.9/site-packages/netmiko/base_connection.py\", line 655, in read_until_pattern
    return self._read_channel_expect(*args, **kwargs)
  File \"/usr/local/lib/python3.9/site-packages/netmiko/base_connection.py\", line 589, in _read_channel_expect
    output += self.read_channel()
  File \"/usr/local/lib/python3.9/site-packages/netmiko/base_connection.py\", line 526, in read_channel
    output = self._read_channel()
  File \"/usr/local/lib/python3.9/site-packages/netmiko/base_connection.py\", line 508, in _read_channel
    output = self.remote_conn.read_very_eager().decode(\"utf-8\", \"ignore\")
  File \"/usr/local/lib/python3.9/telnetlib.py\", line 368, in read_very_eager
    return self.read_very_lazy()
  File \"/usr/local/lib/python3.9/telnetlib.py\", line 405, in read_very_lazy
    raise EOFError(\'telnet connection closed\')
EOFError: telnet connection closed

标签： python telnet netmiko

【解决方案1】：

我发现问题了，在我执行.send_command('y')之前telnet连接是断开的，在我的路由中，输入reload命令后如果收到\n会立即重新加载系统，所以发送后触发了错误.send_command('y')

from nornir import InitNornir
from nornir.core.task import Task, Result 
from nornir_netmiko.tasks.netmiko_send_command import netmiko_send_command

def main():
    
    def task_reboot(task):

      task.run(
          task=netmiko_send_command,
          use_timing=True,
          command_string="reload",
       )
       task.host.close_connections()

    nr = InitNornir(config_file="config.yaml")        
    r1 = nr.filter(device_name="R1")

    try:
        r = r1.run(
            task=task_reboot,
        )
    except EOFError:
        r1.close_connections()
        
if __name__ == "__main__":
    main()

【讨论】：