Exception handling in netmiko

When we design our Python script, we assume that the device is up and running and also that the user has provided the correct credentials, which is not always the case. Sometimes there's a network connectivity issue between Python and the remote device or the user enters the wrong credentials. Usually, python will throw an exception if this happens and will exit, which is not the optimum solution.

The exception handling module in netmiko, netmiko.ssh_exception, provides some exception classes that can handle such situations. The first one is AuthenticationException, and will catch the authentication errors in the remote device. The second class is NetMikoTimeoutException, which will catch timeouts or any connectivity issues between netmiko and the device. What we will need to do is wrap our ConnectHandler() method with the try-except clause and catch timeout and authentication exceptions:

from netmiko import ConnectHandler
from netmiko.ssh_exception import AuthenticationException, NetMikoTimeoutException


device = {
    'device_type': 'cisco_ios',
    'ip': '10.10.88.112',
    'username': 'admin',
    'password': 'access123',
    'secret': 'access123',
}


print "########## Connecting to Device {0} ############".format(device['ip'])
try:
    net_connect = ConnectHandler(**device)
    net_connect.enable()

    print "***** show ip configuration of Device *****"
    output = net_connect.send_command("show ip int b")
    print output

    net_connect.disconnect()

except NetMikoTimeoutException:
    print "=========== SOMETHING WRONG HAPPEN WITH {0} ============".format(device['ip'])

except AuthenticationException:
    print "========= Authentication Failed with {0} ============".format(device['ip'])

except Exception as unknown_error:
    print "============ SOMETHING UNKNOWN HAPPEN WITH {0} ============"