How to generate IP addresses from a CIDR address using Python?

In this article, we will learn how to generate IP addresses from a CIDR (Classless Inter-Domain Routing) address using Python's built-in ipaddress module. CIDR notation represents a network address and its subnet mask, allowing us to define IP address ranges efficiently.

What is CIDR Notation?

CIDR notation combines an IP address with a prefix length (e.g., 192.168.1.0/24). The number after the slash indicates how many bits are used for the network portion, determining the range of available host addresses.

Using IPv4Network

The ipaddress.ip_network() function creates a network object from CIDR notation, allowing us to iterate through all available IP addresses ?

import ipaddress

# Create IPv4 network from CIDR address
network = ipaddress.ip_network('192.168.1.0/29')

print("IPv4 addresses in 192.168.1.0/29:")
for ip in network:
    print(ip)

The output of the above code is ?

IPv4 addresses in 192.168.1.0/29:
192.168.1.0
192.168.1.1
192.168.1.2
192.168.1.3
192.168.1.4
192.168.1.5
192.168.1.6
192.168.1.7

Using IPv6Network

The same approach works for IPv6 addresses with their longer notation ?

import ipaddress

# Create IPv6 network from CIDR address
ipv6_network = ipaddress.ip_network('2001:db8::/125')

print("IPv6 addresses in 2001:db8::/125:")
for ip in ipv6_network:
    print(ip)

The output of the above code is ?

IPv6 addresses in 2001:db8::/125:
2001:db8::
2001:db8::1
2001:db8::2
2001:db8::3
2001:db8::4
2001:db8::5
2001:db8::6
2001:db8::7

Accessing Specific IP Addresses

You can access individual IP addresses using indexing, similar to working with lists ?

import ipaddress

network = ipaddress.ip_network('10.0.0.0/30')

print("First IP address:", network[0])
print("Second IP address:", network[1])
print("Last IP address:", network[-1])
print("Total hosts:", network.num_addresses)

The output of the above code is ?

First IP address: 10.0.0.0
Second IP address: 10.0.0.1
Last IP address: 10.0.0.3
Total hosts: 4

Practical Example: Network Analysis

Here's a practical example showing network information and host generation ?

import ipaddress

def analyze_network(cidr):
    network = ipaddress.ip_network(cidr)
    
    print(f"Network: {network}")
    print(f"Network address: {network.network_address}")
    print(f"Broadcast address: {network.broadcast_address}")
    print(f"Netmask: {network.netmask}")
    print(f"Total addresses: {network.num_addresses}")
    
    print("\nFirst 5 host addresses:")
    for i, ip in enumerate(network):
        if i < 5:
            print(f"  {ip}")
        else:
            break

# Analyze a small network
analyze_network('172.16.10.0/28')

The output of the above code is ?

Network: 172.16.10.0/28
Network address: 172.16.10.0
Broadcast address: 172.16.10.15
Netmask: 255.255.255.240
Total addresses: 16

First 5 host addresses:
  172.16.10.0
  172.16.10.1
  172.16.10.2
  172.16.10.3
  172.16.10.4

Key Methods and Properties

Conclusion

Python's ipaddress module provides a powerful and simple way to work with CIDR addresses. Use ip_network() to create network objects and iterate through all available IP addresses for network planning and analysis.