6 IPv4 Subnetting Practice Free Online FlashCards

Why subnet an IPv4 address block?

Subnetting divides an IPv4 address block into smaller networks, helping organize devices, limit broadcast traffic, and allocate address space to network needs.

What does /24 mean in IPv4 CIDR notation?

IPv4 addresses are 32 bits long. A /24 prefix uses 24 network bits and leaves 8 host bits.

How do subnet-mask bits identify network and host portions?

A subnet mask has 32 bits: leading 1 bits identify the network, and 0 bits identify host addresses. The prefix length counts the leading 1 bits.

How do you calculate total addresses for an IPv4 prefix?

For prefix /p, the host-bit count is $32-p$, so the total address count is $2^{32-p}$.

How are usable hosts counted in ordinary IPv4 subnets?

For ordinary IPv4 subnets, subtract the network and broadcast addresses from the total. A /31 is a point-to-point exception: both addresses can be assigned to endpoints.

How do you find an IPv4 network address?

Keep the network bits and set every host bit to 0. Equivalently, bitwise-AND the IP address with its subnet mask.

How do you find an IPv4 broadcast address?

Keep the network bits and set every host bit to 1.

How do you determine a subnet’s usable host range?

The usable host range starts one address after the network address and ends one address before the broadcast address.

How do you calculate subnet block size within an octet?

When the mask changes within an octet, calculate the block size as $256-\text{mask value}$ in that octet. Subnet network numbers advance by this amount.

Which prefix fits a subnet needing 25 device addresses?

A /27 provides 30 usable host addresses, so it fits 25 devices under the ordinary network-and-broadcast rule.

How many /27 subnets fit in a /24?

A /24 can be divided into eight equal /27 subnets because the prefix gains three network bits: $2^3=8$.

What are the three private IPv4 address ranges?

The private IPv4 ranges are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16.