Bytes, bits and conversions. Relevant for CCNA, Network+, Security+.
Every subnetting shortcut rests on knowing what 192, 224, 240 and 248 look like in binary without thinking, and every IPv6 question rests on hex. Subbing drills single bytes both ways: decimal to 8-bit binary and back, hex to decimal and back, hex straight to binary, mask octets from a count of leading ones, and the value of a given bit.
Easy rounds use the numbers that matter: the powers of two, the mask values and a few round numbers. Medium and hard rounds use any byte.
Generated by the same code as the app. They change with every release; the app never runs out.
Binary and hex for networking: The place values, the eight mask bytes, hex digits and the conversions that make subnetting and IPv6 fast.
11000000. It is 128 + 64, the two highest place values, which is why a /26 mask octet is 192.
C is 12 and 0 is 0, so 12 × 16 + 0 = 192.