SkillCoded

IP Addressing and Subnetting

IPv4 Subnet Masks

Learn how subnet masks separate network and host bits, how CIDR prefix lengths describe masks, and how to calculate whether addresses share a subnet.

Beginner15 min read
IP Addressing and Subnetting lessonNetworkingPractice

UNTIMED COACHING

Practice before the pressure

Use feedback to correct the model, not merely memorize an option position.

GUIDED PRACTICE

Practice the lesson questions

Answer normal lesson questions without a timer. Every answer includes an explanation, and incorrect answers can be tried again before continuing.

CONCEPT MODELS

See the lesson as a system

Use these visual guides to connect the key ideas before answering the questions.

Mask Bits Set the BoundaryIPv4 masks divide network and host roles.
Mask Bits Set the BoundaryAn IPv4 address aligns with mask bits, separating prefix positions from host positions.
IPv4 addressContains network and host positions
Subnet maskMarks prefix and host positions
Network prefixIdentifies the subnet location
Host portionIdentifies a location within subnet
CIDR Maps Bits to OctetsA prefix count becomes a dotted mask.
CIDR Maps Bits to OctetsA CIDR prefix count crosses complete and partial octets before producing a dotted-decimal mask.
CIDR prefixCounts leftmost contiguous one bits
Aligned octetsGroup the thirty-two mask bits
Partial octetHolds a boundary inside octet
Dotted maskExpresses the bit pattern numerically
AND Finds the SubnetLogical AND preserves prefix bits and clears host bits.
AND Finds the SubnetAn address and mask enter logical AND, producing a network address for comparison.
IPv4 addressProvides aligned address bits
Logical ANDCombines corresponding bit positions
Network addressPreserves prefix and clears hosts
Subnet comparisonChecks whether resulting addresses match