In this post, we’ll walk through a Python script that automates the execution of commands on network devices using Paramiko for SSH connections and concurrent.futures for concurrent processing.
Overview of the Script
The script performs the following tasks:
- Establishes SSH connections to network devices.
- Executes a list of commands on each device.
- Saves the output of these commands to separate text files for each device.
- Handles multiple devices concurrently using threading for better performance.
Key Components of the Script
Imports
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| import paramiko
import concurrent.futures
import time
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- paramiko: A Python library for SSH2 connections, used to securely connect to network devices.
- concurrent.futures: Enables concurrent execution of function calls using threads or processes.
- time: Provides time-related functions, like sleeping for a few seconds between operations.
Function: execute_commands_on_device
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| def execute_commands_on_device(hostname, username, password, commands, output_file):
try:
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(hostname, username=username, password=password)
channel = ssh.invoke_shell()
time.sleep(1) # Allow time for the shell to be ready
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- Establishes an SSH connection: The paramiko.SSHClient() is used to create an SSH client, and the connection is established with the connect() method.
- Handles unknown host keys: The AutoAddPolicy() automatically adds the host key without manual intervention.
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| with open(output_file, 'w') as f:
for command in commands:
channel.send(command + "\n")
time.sleep(2) # Wait for the command to be executed and output to be generated
output = ""
while channel.recv_ready():
output += channel.recv(1024).decode()
# Write output to the file
f.write(f"Command: {command}\n")
f.write(f"Output:\n{output}\n")
f.write("\n" + "-"*50 + "\n\n")
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- Command execution: Sends each command to the device and waits briefly for the output.
- Captures and writes output: Reads the command’s output from the device and writes it to the specified output file.
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| channel.close()
ssh.close()
except Exception as e:
print(f"Failed to execute commands on {hostname}: {str(e)}")
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- Error handling: Catches any exceptions during the connection or command execution process and logs an error message.
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| def main():
# Enable Paramiko logging
paramiko.util.log_to_file('paramiko.log')
devices = [
{"hostname": "sandbox-iosxe-recomm-1.cisco.com",
"username": "admin",
"password": "C1sco12345"},
{"hostname": "sandbox-iosxr-1.cisco.com",
"username": "admin",
"password": "C1sco12345"}
]
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- Device list: Contains dictionaries with the hostname, username, and password for each device.
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| commands = [
'term len 0',
'show version',
'show ip interface brief',
'show running-config'
]
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- Commands list: A list of CLI commands to be executed on each device.
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| with concurrent.futures.ThreadPoolExecutor() as executor:
futures = []
for device in devices:
output_file = f"{device['hostname']}_output.txt"
futures.append(executor.submit(execute_commands_on_device, device['hostname'], device['username'], device['password'], commands, output_file))
for future in concurrent.futures.as_completed(futures):
if future.exception() is not None:
print(f"Execution generated an exception: {future.exception()}")
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- Concurrency: Uses ThreadPoolExecutor to execute commands on multiple devices in parallel, improving efficiency.
- Error reporting: Logs any exceptions encountered during execution.
Conclusion
This script showcases how to automate network management tasks using Python. By leveraging Paramiko for secure SSH connections and concurrent.futures for concurrency, network administrators can efficiently manage multiple devices, run diagnostics, and collect configurations.
Devices
For this demo we will take advantage of always ON cisco devices available at (Devnet website) https://developer.cisco.com/
| IOS-XE |
|---|
| sandbox-iosxe-recomm-1.cisco.com |
| IOS-XR |
|---|
| sandbox-iosxr-1.cisco.com |
You can test the script right away—just copy the code, install Paramiko in your environment and you are good to go!
Code
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| import paramiko
import concurrent.futures
import time
def execute_commands_on_device(hostname, username, password, commands, output_file):
try:
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(hostname, username=username, password=password)
channel = ssh.invoke_shell()
time.sleep(1) # Allow time for the shell to be ready
with open(output_file, 'w') as f:
for command in commands:
channel.send(command + "\n")
time.sleep(2) # Wait for the command to be executed and output to be generated
output = ""
while channel.recv_ready():
output += channel.recv(1024).decode()
# Write output to the file
f.write(f"Command: {command}\n")
f.write(f"Output:\n{output}\n")
f.write("\n" + "-"*50 + "\n\n")
channel.close()
ssh.close()
except Exception as e:
print(f"Failed to execute commands on {hostname}: {str(e)}")
def main():
# Enable Paramiko logging
paramiko.util.log_to_file('paramiko.log')
devices = [
{"hostname": "sandbox-iosxe-recomm-1.cisco.com",
"username": "admin",
"password": "C1sco12345"},
{"hostname": "sandbox-iosxr-1.cisco.com",
"username": "admin",
"password": "C1sco12345"}
]
commands = [
'term len 0',
'show version',
'show ip interface brief',
'show running-config'
]
with concurrent.futures.ThreadPoolExecutor() as executor:
futures = []
for device in devices:
output_file = f"{device['hostname']}_output.txt"
futures.append(executor.submit(execute_commands_on_device, device['hostname'], device['username'], device['password'], commands, output_file))
for future in concurrent.futures.as_completed(futures):
if future.exception() is not None:
print(f"Execution generated an exception: {future.exception()}")
if __name__ == '__main__':
main()
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References
