Guides and practice
Short guides for the methods, and a practice page per topic with sample questions and the working. The app generates the rest.
Practice by topic
Subnetting practiceMasks, ranges and hosts · CCNA, Network+IPv6 practiceNotation, types, EUI-64 · CCNA, Network+Port numbers quizWell-known ports, TCP vs UDP · Network+, Security+, CCNAVLSM practiceSize, split and summarise subnets · CCNABinary and hex practiceBytes, bits and conversions · CCNA, Network+, Security+ACL wildcard mask practiceWildcard masks and matching · CCNA, Security+Linux permissions quizchmod, octal, umask · Linux+, RHCSA, Security+
Guides
How to subnet fastThe block size method for IPv4 subnetting: interesting octet, block size, network, broadcast and host range in under ten seconds, with worked examples.Wildcard masks explainedWhat a wildcard mask is, how it relates to a subnet mask, how to compute one for any network, and how Cisco ACLs use host and any.IPv6 address compressionHow to write an IPv6 address in its shortest valid form, the mistakes exams test for, and how to expand a compressed address back to eight groups.Linux file permissionsRead and write Linux permission modes: the three digits, rwx triplets, umask arithmetic, symbolic chmod, setuid, setgid and the sticky bit.Binary and hex for networkingThe place values, the eight mask bytes, hex digits and the conversions that make subnetting and IPv6 fast.VLSM and route summarisationSizing subnets for host counts, carving a block into subnets, finding the nth subnet, and summarising contiguous networks into one route.
Ports cheat sheetAll 146 ports, grouped by set, with transport and notes.