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CompTIA Network+ 1.7 Cisco CCNA 1.6 Cisco CCST Networking 2.2
TechKnowSurge Catalog Interactives Class C Subnet Range Calculator
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Class C Subnet Range Calculator

Subnet a Class C network to a stated need, then type the network, broadcast and usable range of a numbered subnet.

⚑ Complete this interactive to capture a CTF flag worth 5 points.

About this interactive

A Class C network has one octet of host bits to borrow from. Borrowing b bits gives 2^b subnets, and the bits left decide the size of each: borrow 2 and each subnet is 64 addresses; borrow 3 and each is 32. The subnets sit end to end. The first starts at the network you were given, and each one after it starts one block further on, so with 32-address blocks the network addresses are .0, .32, .64, .96 and so on. Inside each block the first address, with every host bit 0, is the network address; the last, with every host bit 1, is the broadcast address; everything between is usable. To check your work, the broadcast address of one subnet is always one below the network address of the next. Where you are given several networks of different sizes, plan every subnet for the largest one: a single mask makes them all the same size, and the smaller networks simply leave addresses spare. Sizing each subnet to its own network is variable-length subnet masking, which comes later. Type addresses in dotted decimal and counts in digits. Anything you miss shows the answer and how to work it out. Seven of the twenty-three questions are drawn each run.

What you'll learn

Aligned to

CompTIA Network+
1.7 Given a scenario, use appropriate IPv4 network addressing.
Cisco CCNA
1.6 Configure and verify IPv4 addressing and subnetting
Cisco CCST Networking
2.2 Identify IPv4 addresses and subnet formats

Key terms

Network Address
The first address in an IP network range that identifies the network itself and cannot be assigned to a host. It is formed when all host bits are set to zero.
Broadcast Address
The last address in an IP subnet range, formed when all host bits are set to one, used to send a single packet to every device on that network simultaneously.
Usable Host Range
The set of IP addresses within a subnet that can actually be assigned to network devices, spanning from one address above the network address to one address below the broadcast address. For example, in the 192.168.1.0/24 network, the usable host range is 192.168.1.1 through 192.168.1.254.
Custom Subnet Mask
A subnet mask that draws the network/host boundary at a point other than the classful boundary, allowing flexible division of network and host bits.
Borrowed Bits
Host bits reallocated to the network portion of a subnet mask to create additional subnets, reducing the number of available hosts per subnet.
Subnet
A logical subdivision of an IP network, used to organize and segment network traffic.

Topics

Subnetting Network Address Broadcast Address Usable Host Range Interactive Calculation

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