CCNA Network Infrastructure and Connectivity Practice Question
A subnet has the network address 192.168.20.128/26. What is the broadcast address?
⚠ Common exam trap
Be careful not to confuse the broadcast address with the first address of the next subnet or with the broadcast address of a different subnet mask.
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
✓
192.168.20.191
A /26 subnet uses blocks of 64 addresses. In plain language, the block that starts at 192.168.20.128 runs through 192.168.20.191. The first address in that block is the network address, and the last address is the broadcast address. That means the broadcast address is 192.168.20.191. This is a standard subnetting calculation. Once the block size is identified, the broadcast address is simply the last address in the block.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
192.168.20.159
Why it's wrong here
192.168.20.159 is the broadcast address for a /27 subnet (192.168.20.128/27) which covers .128-.159, not for the /26 subnet in question. A /26 block is larger (64 addresses), extending from .128 to .191, so its broadcast must be .191, not .159.
When this WOULD be correct
If the question specified a subnet mask of /25 instead of /26, the network address would be 192.168.20.128 and the broadcast address would then be 192.168.20.159, making this option correct.
- ✓
192.168.20.191
Why this is correct
192.168.20.191 is the broadcast address for the 192.168.20.128/26 subnet. A /26 prefix leaves 6 host bits (32-26=6), yielding 2^6=64 addresses per subnet. Starting at network address .128, the valid addresses run from .129 through .190, and .191 is the final address (broadcast) before the next subnet begins at .192.
- ✗
192.168.20.192
Why it's wrong here
192.168.20.192 is incorrect because it is the network address of the next /26 subnet, not part of the .128/26 range. The subnet spanning .128 through .191 uses only 64 addresses, so .192 is the first address outside that block, signaling the start of the following subnet (192.168.20.192/26).
When this WOULD be correct
If the question specified a different subnet, such as 192.168.20.192/26, then option C would be the correct broadcast address for that subnet, as it would encompass the range from 192.168.20.192 to 192.168.20.255.
- ✗
192.168.20.255
Why it's wrong here
192.168.20.255 is the broadcast of the entire class C /24 network (192.168.20.0/24), which can be divided into four /26 subnets. The specific subnet 192.168.20.128/26 only encompasses addresses .128 through .191, so its broadcast is .191; .255 belongs to the last /26 range (.192-.255), not this one.
When this WOULD be correct
If the question asked for the broadcast address of the entire 192.168.20.0/24 network instead of the specific /26 subnet, then 192.168.20.255 would be the correct answer, as it serves as the broadcast address for that larger subnet.
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.
✓192.168.20.191Correct answer▾
Why this is correct
192.168.20.191 is the broadcast address for the 192.168.20.128/26 subnet. A /26 prefix leaves 6 host bits (32-26=6), yielding 2^6=64 addresses per subnet. Starting at network address .128, the valid addresses run from .129 through .190, and .191 is the final address (broadcast) before the next subnet begins at .192.
✗192.168.20.159Wrong answer — click to see why▾
Why this is wrong here
Option A (192.168.20.159) is incorrect because the broadcast address for the subnet 192.168.20.128/26 is 192.168.20.191, calculated as the highest address in the subnet range from 192.168.20.128 to 192.168.20.191.
★ When this WOULD be the correct answer
If the question specified a subnet mask of /25 instead of /26, the network address would be 192.168.20.128 and the broadcast address would then be 192.168.20.159, making this option correct.
Why candidates choose this
Candidates may choose this option due to confusion between subnet ranges, mistakenly calculating the broadcast address by incorrectly interpreting the subnet mask or misaligning the address range.
✗192.168.20.192Wrong answer — click to see why▾
Why this is wrong here
The option C, 192.168.20.192, is incorrect because it falls outside the range of the subnet defined by 192.168.20.128/26, which has a valid broadcast address of 192.168.20.191.
★ When this WOULD be the correct answer
If the question specified a different subnet, such as 192.168.20.192/26, then option C would be the correct broadcast address for that subnet, as it would encompass the range from 192.168.20.192 to 192.168.20.255.
Why candidates choose this
Candidates might choose this option due to confusion between the subnet address and the broadcast address, especially if they miscalculate the range or overlook the CIDR notation.
✗192.168.20.255Wrong answer — click to see why▾
Why this is wrong here
The broadcast address for the subnet 192.168.20.128/26 is 192.168.20.191, not 192.168.20.255. The address 192.168.20.255 is the broadcast address for the entire 192.168.20.0/24 network, which is not relevant to the specified subnet.
★ When this WOULD be the correct answer
If the question asked for the broadcast address of the entire 192.168.20.0/24 network instead of the specific /26 subnet, then 192.168.20.255 would be the correct answer, as it serves as the broadcast address for that larger subnet.
Why candidates choose this
Candidates may choose this option due to familiarity with the concept of broadcast addresses, often associating the highest address in a subnet with the broadcast address without considering the specific subnet mask provided.
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
Learn chapter
IPv4 Addressing and Address Classes
Key term
Subnetting
Subnetting is the process of dividing a larger IP network into smaller, more manageable subnetworks (subnets) to improve performance, security, and efficient use of IP addresses.
Key term
Block size
Block size is the amount of data, measured in bytes, that a system reads or writes in a single operation, affecting storage efficiency and network performance.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.