A network administrator is assigned the IPv4 address block 10.50.0.0/22 to provision subne… — Cisco CCNA

A network administrator is assigned the IPv4 address block $10.50.0.0/22$ to provision subnets for an enterprise IP telephony deployment. Each subnet requires support for at least $50$ usable host IP addresses. If the administrator subnets the entire $10.50.0.0/22$ block using a uniform prefix length that meets this host requirement with minimal wasted host space, how many total subnets can be created?

Answer: 16 subnets

Answer

16 subnets can be created from the block.

To support at least 50 usable host IP addresses per subnet, 6 host bits are needed (

2^6 - 2 = 62

usable IPs), which corresponds to a /26 prefix length (

32 - 6 = 26

). Borrowing bits from the parent /22 prefix to create /26 subnets uses

26 - 22 = 4

subnet bits, resulting in

2^4 = 16

total subnets.

Step-by-Step Solution

Calculate the number of host bits required for 50 usable IP addresses

6 host bits are required

The formula for usable host IPs is

2^h - 2

. With

h = 5

2^5 - 2 = 30

hosts (insufficient). With

h = 6

2^6 - 2 = 62

usable hosts, which satisfies the requirement of at least 50 hosts.

Determine the new subnet prefix length

The prefix length is /26

Subtracting the 6 host bits from the 32-bit IPv4 address space yields

32 - 6 = 26

Calculate the number of subnets derived from the parent /22 block

16 subnets

Subtracting the original prefix (/22) from the new prefix (/26) gives

26 - 22 = 4

subnet bits. Borrowing 4 bits produces

2^4 = 16

subnets.

Key Concept

Subnet sizing and calculation of total subnets created using FLSM from a CIDR block.

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