You've stated a foundational fact about CIDR notation and subnet masks. Let me verify the claim: **255 in binary:** 11111111 ✓ (correct — 128+64+32+16+8+4+2+1 = 255) **0 in binary:** 00000000 ✓ (correct — all bits zero) **255.255.255.0 in binary:** 11111111.11111111.11111111.00000000 ✓ (correct) This is a **/24 subnet mask** — the first 24 bits are "network" (all 1s), the last 8 bits are "host" (all 0s). It defines a Class C network with 256 total addresses (254 usable for hosts, after excluding network and broadcast addresses).

IPv4 is a 32-bit address split into four 8-bit chunks so humans can actually read it. Each octet goes from 0 to 255.

A /24 uses 24 mask bits and 8 host bits. The highest host-bit value is 2^7 = 128. The full host range is 2^8 = 256 addresses.

Once you can read binary octets at a glance, network and broadcast become trivial: AND with the mask for network, OR with the inverted mask for broadcast.