Python3 ncclient/paramiko连接Cisco Nexus报错：_RSAPublicKey无verify属性

Hey DanM, this is a common compatibility issue I’ve seen pop up with older Ubuntu environments and Python NETCONF libraries—let’s work through fixing it step by step.

Root Cause #

The AttributeError: '_RSAPublicKey' object has no attribute 'verify' error almost always comes down to incompatible versions of the cryptography library. Ubuntu 16.04 LTS ships with an outdated cryptography version (usually around 1.2.3), while newer releases of ncclient (the Python library handling NETCONF connections) rely on updated cryptography APIs that changed how RSA public key verification works.

Step-by-Step Fix #

1. Check your current cryptography version
   Run this command to confirm which version you have installed:

   pip3 show cryptography
   

   If the version is older than 2.5, that’s definitely the culprit here.

2. Upgrade cryptography to a compatible stable version
   Ubuntu 16.04’s Python 3.5 doesn’t support the latest cryptography releases, so install a version that plays nice with both your system and ncclient:

   pip3 install --user --upgrade cryptography==3.4.8
   

   The --user flag installs the package to your personal user directory, avoiding permission issues with system-level packages.

3. Update ncclient to a matching compatible version
   Pair the upgraded cryptography with a stable ncclient release that supports it:

   pip3 install --user --upgrade ncclient==0.6.13
   

4. Test your connection code
   Modify your existing code to run a basic test (adjust credentials and device IP as needed):

   from ncclient import manager
   
   def connect_to_nexus():
       try:
           with manager.connect(
               host="192.168.1.100",  # Replace with your Nexus device IP
               port=830,
               username="admin",
               password="your-secure-password",
               hostkey_verify=False,  # Disable only for testing; enable in production
               device_params={'name': 'nexus'}
           ) as session:
               print("Connection successful!")
               # Example: Fetch running configuration
               config = session.get_config(source='running')
               print(config)
       except Exception as e:
           print(f"Connection failed: {str(e)}")
   
   connect_to_nexus()
   

   Note: Disabling hostkey_verify is for testing purposes only—for production use, make sure you have the device’s host key properly configured.

If you still hit snags, double-check that you’re using the correct Python 3 environment (run which python3 to confirm) and that no system-level packages are overriding your user-installed libraries.

内容的提问来源于stack exchange，提问作者DanM