Subnetting: From First Principles to VLSM
Subnetting is one of those skills that seems intimidating until it clicks, and then it feels obvious. This post builds from first principles — binary representation, masks, and block sizes — through variable-length subnet masking (VLSM) and summarization. IP Address Structure An IPv4 address is 32 bits divided into two logical parts: network and host. 192.168.10.25 = 11000000.10101000.00001010.00011001 The subnet mask defines the split. A 255.255.255.0 mask (or /24 in CIDR) means the first 24 bits identify the network, the last 8 identify the host. ...