IP Networking Guides.
Free, in-depth guides on subnetting, CIDR notation, IPv4 and IPv6 — written for network engineers, students, and developers.
What is a Subnet Mask?
Learn what subnet masks are, how they work, and why every IP network depends on them.
Read guideCIDR Notation Explained
Understand CIDR (Classless Inter-Domain Routing) notation, how prefix lengths work, and how to convert between CIDR and subnet masks.
Read guideSubnetting Tutorial: How to Subnet a Network
A step-by-step guide to subnetting — dividing a large network into smaller subnets using VLSM and CIDR.
Read guideIPv4 vs IPv6: Key Differences Explained
Compare IPv4 and IPv6 addressing — structure, notation, address space, and how to use our IPv6 calculator.
Read guideWildcard Masks: What They Are and How to Use Them
Learn what wildcard masks are, how they differ from subnet masks, and where they are used in Cisco ACLs and OSPF.
Read guidePrivate IP Address Ranges (RFC 1918)
Everything you need to know about private IPv4 address ranges — 10.x, 172.16.x, 192.168.x — and when to use each.
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