Practical technology guides
Understand network basics, domain records, security hygiene and data workflows.
How to summarize an IP range into CIDR blocks
Represent an IPv4 start and end address as the smallest set of exact CIDR blocks.
Read guideIPv6 prefixes and subnet ranges explained
Understand IPv6 CIDR prefixes, compressed notation, address ranges and why IPv6 has no broadcast address.
Read guideMAC address formats and randomized addresses
Read a MAC address format and understand its unicast, multicast and local-administration bits.
Read guideIPv4 subnet masks and CIDR explained
Understand network addresses, broadcast addresses, host ranges and /31 or /32 edge cases.
Read guideHow to calculate percentage change
Find a percentage increase or decrease, and see why the starting value matters.
Read guideHow to compare spreadsheets when rows have moved
Use a stable identifier to distinguish real data changes from a different row order.
Read guideKeep leading zeros when converting CSV to Excel
Why identifiers such as 00123 change, and how text cells help preserve them.
Read guideMerge CSV files with different column orders
Match headings instead of column positions, and understand what happens to missing columns.
Read guideWhat a CSV cleaner can safely fix
Separate predictable formatting cleanup from changes that require human judgment.
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