Subnet Calc

CIDR/subnet calculator CLI. IPv4 and IPv6 support with no external dependencies.

Quick Start

# Basic subnet calculation
python3 scripts/subnet_calc.py 192.168.1.0/24

# JSON output
python3 scripts/subnet_calc.py 10.0.0.0/8 -f json

# Check if IP is in a network
python3 scripts/subnet_calc.py 172.16.0.0/16 --contains 172.16.5.10

# Split into smaller subnets
python3 scripts/subnet_calc.py 192.168.0.0/22 --split 24

# IPv6
python3 scripts/subnet_calc.py 2001:db8::/32

Output Fields (IPv4)

• CIDR — Normalized CIDR notation
• Network/Broadcast Address — First and last address in the range
• Subnet Mask / Wildcard Mask — Standard and inverted masks
• Total Addresses / Usable Hosts — Address count minus network and broadcast
• First/Last Host — Usable host range
• Binary representations — Network and mask in binary
• Flags — Private, loopback, multicast, link-local detection

Options

Notes

• Python 3 stdlib only (uses ipaddress module)
• Handles /31 (RFC 3021 point-to-point) and /32 correctly
• Input is normalized with strict=False (host bits are masked)