Cisco IOU images require a valid license key to function in network simulators like GNS3, EVE-NG, or PNET LAB. CiscoIOUKeygen.py is a Python-based tool that securely generates host-specific license keys, enabling you to deploy Cisco lab images for learning, testing, and professional certification preparation.

1️⃣ Prerequisites for Using CiscoIOUKeygen.py

• Python installed (version 2.7 or 3.x compatible)
• Access to the CiscoIOUKeygen.py script from a reputable source
• Administrative permissions to write license files to $HOME/.iourc
• Understanding of your simulator environment: GNS3, EVE-NG, or PNET LAB
• Basic knowledge of hostnames and system hostid retrieval

2️⃣ Step-by-Step Cisco IOU License Generation

Follow these steps to generate a license key and apply it to your IOU image:

1. Download CiscoIOUKeygen.py and place it in your working directory.
2. Open a terminal or command prompt and navigate to the script location.
3. Run the generator with: python CiscoIOUKeygen.py
4. Enter the hostname and feature set for your IOU image.
5. The script outputs a license key tailored to your system.
6. Create or update the license file: $HOME/.iourc with the generated key.
7. Optional: disable Cisco phone-home to prevent connectivity checks:

grep -q -F '127.0.0.1 xml.cisco.com' /etc/hosts || echo '127.0.0.1 xml.cisco.com' | sudo tee -a /etc/hosts

3️⃣ CiscoIOUKeygen.py Example Script

#! /usr/bin/python
print ("\n**************************************************************")
print "Cisco IOU License Generator - Python Version"
import os, socket, hashlib, struct

hostid = os.popen("hostid").read().strip()
hostname = socket.gethostname()
ioukey = int(hostid, 16)
for x in hostname:
    ioukey += ord(x)

iouPad1 = '\x4B\x58\x21\x81\x56\x7B\x0D\xF3\x21\x43\x9B\x7E\xAC\x1D\xE6\x8A'
iouPad2 = '\x80' + 39*'\0'
md5input = iouPad1 + iouPad2 + struct.pack('!L', ioukey) + iouPad1
iouLicense = hashlib.md5(md5input).hexdigest()[:16]

print ("Create the license file $HOME/.iourc with this content:")
print ("[license]\n" + hostname + " = " + iouLicense + ";")
print ("Disable phone-home with:")
print ("127.0.0.1 xml.cisco.com >> /etc/hosts")

4️⃣ Legal & Security Considerations

Always adhere to vendor licensing policies:

• Use legally obtained Cisco IOU images.
• Do not distribute license keys publicly.
• Run the generator in isolated lab environments.
• Consider SNMPv3 and secure monitoring if deploying in enterprise virtual labs.

CiscoIOUKeygen.py generates valid Cisco IOU license keys for GNS3, EVE-NG, and PNET LAB.

5️⃣ Advanced Tips for CCNA & CCNP Lab Builders

• Combine CiscoIOUKeygen.py with CLI traffic monitoring to test QoS and NetFlow within your lab.
• Integrate license generation with automated Python scripts for batch lab deployments.
• Document each lab node hostname & license to maintain internal compliance.
• Use internal linking to cluster content like GUI Traffic Monitoring and SNMP Monitoring for scalability.