Guides
Short, practical explanations of the networking concepts behind our tools.
What Is an IP Address?Learn what an IP address is, how IPv4 and IPv6 differ, which ranges are private (RFC 1918, CGNAT), how NAT works and how to find your own IP address.Subnet Mask and CIDR ExplainedLearn how subnet masks and CIDR notation work, with a worked /26 example, a full /8 to /32 cheat sheet, wildcard masks and IPv6 /48, /56 and /64 rules.The OSI Model: 7 Layers ExplainedThe OSI model has seven layers, from physical to application. Learn each layer, how it maps to TCP/IP, and which layer ping, DNS, TLS and port checks test.Well-Known Ports and What They MeanWhat network ports are, TCP vs UDP, port ranges, how to test if a port is open, closed or filtered, and which ports you should never expose to the internet.How DNS WorksDNS turns domain names into IP addresses. See the resolution path, record types, caching and TTL, what DNS propagation is, and how to spread changes fast.