CCNA Network Infrastructure and Connectivity Practice Question
A branch office needs four subnets from the 192.168.50.0/24 network, with each subnet supporting up to 50 hosts. Which prefix length should be used for each subnet?
⚠ Common exam trap
A frequent exam trap is selecting a subnet mask that provides enough hosts but not enough subnets, or vice versa. For instance, choosing /25 seems tempting because it supports 126 hosts, which exceeds the 50-host requirement. However, /25 only creates two subnets from a /24, which fails the requirement for four subnets. Another trap is picking /27, which creates enough subnets but only supports 30 hosts, insufficient for 50 hosts per subnet. Candidates must carefully balance subnet count and host capacity to avoid these pitfalls.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
/26
Each subnet must support at least 50 hosts, so /26 is the smallest suitable prefix because it provides 62 usable addresses. A /24 can be split into exactly four /26 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
/25
Why it's wrong here
A /25 prefix borrows only 1 host bit from the /24, which produces just 2 subnets (2^1 = 2), not the required four. Although each /25 subnet supports 126 usable hosts (2^7 - 2), the subnet count is insufficient. This option fails because it under-subnets the address space despite adequate host capacity.
When this WOULD be correct
In a scenario where a network engineer needs to create two subnets from a /24 network, each supporting up to 126 hosts, option A (/25) would be correct. This would allow for two subnets, each with sufficient capacity for a larger number of hosts than required.
- ✓
/26
Why this is correct
A /26 prefix borrows 2 host bits from the /24, yielding 4 equal-sized subnets (2^2 = 4), each with 62 usable addresses (2^6 - 2 = 62). This exactly meets the branch office requirement for four subnets while providing sufficient host capacity for typical devices. The subnet mask 255.255.255.192 is the correct choice.
- ✗
/27
Why it's wrong here
A /27 prefix borrows 3 host bits, creating 8 subnets (2^3 = 8), which exceeds the needed four subnets. However, each subnet only provides 30 usable hosts (2^5 - 2), which is too few for a branch office that likely needs more than 30 addresses per subnet. The host shortage makes /27 impractical, even though the subnet count is acceptable.
When this WOULD be correct
In a scenario where the requirement is to create subnets for a network that only needs to support up to 30 hosts each, such as a small office with limited devices, /27 would be the correct choice as it allows for 30 usable addresses per subnet.
- ✗
/28
Why it's wrong here
A /28 prefix borrows 4 host bits, resulting in 16 subnets (2^4 = 16) but only 14 usable hosts per subnet (2^4 - 2). This is extremely restrictive and far below the host requirements for a branch office subnet. /28 over-fragments the /24, providing far more subnets than needed while starving each subnet of usable addresses.
When this WOULD be correct
In a different scenario where a network administrator needs to create multiple subnets for a small office with a maximum of 14 hosts each, using the 192.168.50.0/24 network, a /28 subnet would be appropriate as it allows for 16 IP addresses, accommodating the host requirement.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓/26Correct answer▾
Why this is correct
A /26 prefix borrows 2 host bits from the /24, yielding 4 equal-sized subnets (2^2 = 4), each with 62 usable addresses (2^6 - 2 = 62). This exactly meets the branch office requirement for four subnets while providing sufficient host capacity for typical devices. The subnet mask 255.255.255.192 is the correct choice.
✗/25Wrong answer — click to see why▾
Why this is wrong here
A /25 prefix length creates only two subnets from a /24 network, not the required four subnets. While each subnet would support up to 126 hosts, the requirement is for four subnets, so /25 does not meet the subnet count requirement.
★ When this WOULD be the correct answer
In a scenario where a network engineer needs to create two subnets from a /24 network, each supporting up to 126 hosts, option A (/25) would be correct. This would allow for two subnets, each with sufficient capacity for a larger number of hosts than required.
Why candidates choose this
Students might choose /25 because it provides more than enough hosts per subnet (126 usable addresses) and they may overlook the requirement for exactly four subnets, focusing only on the host count.
✗/27Wrong answer — click to see why▾
Why this is wrong here
A /27 prefix length provides only 30 usable host addresses per subnet (32 total addresses minus network and broadcast), which is insufficient for supporting up to 50 hosts. Although it can create eight subnets from a /24, the host count per subnet is too low.
★ When this WOULD be the correct answer
In a scenario where the requirement is to create subnets for a network that only needs to support up to 30 hosts each, such as a small office with limited devices, /27 would be the correct choice as it allows for 30 usable addresses per subnet.
Why candidates choose this
Students might choose /27 because it can create more than four subnets, and they may incorrectly assume that more subnets are better or forget to verify the host capacity per subnet.
✗/28Wrong answer — click to see why▾
Why this is wrong here
A /28 prefix length yields only 14 usable host addresses per subnet (16 total addresses minus network and broadcast), which is far below the required 50 hosts per subnet. It creates 16 subnets from a /24, but the host count is inadequate.
★ When this WOULD be the correct answer
In a different scenario where a network administrator needs to create multiple subnets for a small office with a maximum of 14 hosts each, using the 192.168.50.0/24 network, a /28 subnet would be appropriate as it allows for 16 IP addresses, accommodating the host requirement.
Why candidates choose this
Students might choose /28 if they focus solely on the number of subnets (16 subnets easily exceeds the requirement of four) without considering the host capacity per subnet, or they may confuse the host calculation with a different prefix length.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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Related to this question
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Network Topology Types
Key term
Subnet
A subnet is a logical subdivision of an IP network, created by partitioning a larger network address space using subnet masks.
Key term
CAN
A CAN (Controller Area Network) is a robust vehicle bus standard designed to allow microcontrollers and devices to communicate with each other without a host computer.
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