Lion Cipher Lab
Design an IP addressing plan with VLSM and verify it in Python
- Cyber / Security Engineer
- Intermediate
- ~50 min
- Free · no account required
Why it matters
Network segmentation is one of the most effective security controls there is. It keeps the guest Wi-Fi away from the payroll server and the cameras away from everything. Every segment needs its own subnet, and the addressing plan decides whether segmentation stays clean or degrades over time. A plan with no growth room forces someone, a year later, to bolt on a second range or widen a subnet into its neighbour. An overlapping or misaligned subnet makes firewall rules match traffic they were never meant to match. An undocumented plan means nobody can tell which address belongs to which zone…
What you'll learn
- private address space (RFC 1918) and CIDR notation
- sizing a subnet from a host count, with growth
- variable-length subnet masking (VLSM), largest first
- why subnets must sit on aligned boundaries
- checking a plan for overlaps, misalignment and out-of-block subnets
- using Python's ipaddress module
- why an addressing plan is a security artifact
Steps in this lab
- Addresses, prefixes and private space
- Size each segment, with growth
- Write the planner and checker
- Plan it: the /22 is too small, the /21 fits
- Check a hand-written plan
- Make the plan a security artifact