CCNA Network Infrastructure and Connectivity Practice Question
This 200-301 practice question tests your understanding of network infrastructure and connectivity. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. A key principle to apply: a /26 subnet mask divides an IP network into blocks of 64 addresses, including network and broadcast addresses.. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A host is configured as 172.16.20.190/26. Which range contains the usable host addresses for that subnet?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
172.16.20.129 to 172.16.20.190
A /26 uses blocks of 64 addresses. In practical terms, the fourth-octet ranges are 0–63, 64–127, 128–191, and 192–255. Since 190 falls inside the 128–191 block, the network address is .128 and the broadcast address is .191. That leaves .129 through .190 as the usable range.
This is a strong test of whether you can identify the correct block and then exclude the reserved boundary addresses correctly.
Key principle: A /26 subnet mask divides an IP network into blocks of 64 addresses, including network and broadcast addresses.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
172.16.20.129 to 172.16.20.190
Why this is correct
This is correct because .128 is the network and .191 is the broadcast.
Related concept
A /26 subnet mask divides an IP network into blocks of 64 addresses, including network and broadcast addresses.
✗
172.16.20.128 to 172.16.20.191
Why it's wrong here
This is wrong because those include the reserved network and broadcast addresses.
When this WOULD be correct
If the question asked for the range of all IP addresses within the subnet, including the network and broadcast addresses, then option B would be correct, as it would encompass the entire range from 172.16.20.128 to 172.16.20.191.
✗
172.16.20.130 to 172.16.20.191
Why it's wrong here
This is wrong because it excludes one valid host and includes the broadcast address.
When this WOULD be correct
If the question specified a subnet mask of /25 instead of /26, the usable host range would be 172.16.20.129 to 172.16.20.254, making option C correct as it would then include valid host addresses within that range.
✗
172.16.20.193 to 172.16.20.254
Why it's wrong here
This is wrong because that range belongs to the next subnet block.
When this WOULD be correct
If the question specified a different subnet, such as 172.16.20.192/26, then option D would be correct, as it would represent the usable host addresses within that subnet range.
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.
✓172.16.20.129 to 172.16.20.190Correct answer▾
Why this is correct
This is correct because .128 is the network and .191 is the broadcast.
✗172.16.20.128 to 172.16.20.191Wrong answer — click to see why▾
Why this is wrong here
Option B is incorrect because it includes the network address (172.16.20.128) and the broadcast address (172.16.20.191) for the subnet, which are not usable host addresses.
★ When this WOULD be the correct answer
If the question asked for the range of all IP addresses within the subnet, including the network and broadcast addresses, then option B would be correct, as it would encompass the entire range from 172.16.20.128 to 172.16.20.191.
Why candidates choose this
Candidates may choose this option because it closely resembles the correct range and includes the last usable address, leading to confusion between usable and total address ranges in subnetting.
✗172.16.20.130 to 172.16.20.191Wrong answer — click to see why▾
Why this is wrong here
Option C is incorrect because it includes the address 172.16.20.191, which is the broadcast address for the subnet 172.16.20.128/26, making it unusable for hosts.
★ When this WOULD be the correct answer
If the question specified a subnet mask of /25 instead of /26, the usable host range would be 172.16.20.129 to 172.16.20.254, making option C correct as it would then include valid host addresses within that range.
Why candidates choose this
Candidates may choose option C due to confusion about subnet boundaries, mistakenly thinking that the broadcast address can be included in the usable range, especially if they miscalculate the subnet mask.
✗172.16.20.193 to 172.16.20.254Wrong answer — click to see why▾
Why this is wrong here
Option D is incorrect because the specified range (172.16.20.193 to 172.16.20.254) falls outside the subnet defined by 172.16.20.190/26, which only includes addresses from 172.16.20.128 to 172.16.20.191.
★ When this WOULD be the correct answer
If the question specified a different subnet, such as 172.16.20.192/26, then option D would be correct, as it would represent the usable host addresses within that subnet range.
Why candidates choose this
Candidates might choose this option due to a misunderstanding of subnetting boundaries, mistakenly believing that addresses beyond the subnet's defined range could still be valid host addresses.
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?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is selecting an answer range that includes the network or broadcast address as usable hosts. For example, option B lists 172.16.20.128 to 172.16.20.191, which incorrectly includes the network (.128) and broadcast (.191) addresses. These addresses are reserved and cannot be assigned to hosts. Another trap is excluding valid host addresses or including addresses from adjacent subnets, as seen in options C and D. Misidentifying subnet boundaries or forgetting to exclude reserved addresses causes these errors, leading to incorrect subnetting answers.
Detailed technical explanation
How to think about this question
Subnetting divides an IP network into smaller logical segments called subnets, each with its own network address and broadcast address. A /26 subnet mask means the first 26 bits are fixed for the network portion, leaving 6 bits for host addresses. This results in 64 IP addresses per subnet (2^6 = 64), including the network and broadcast addresses. The usable host range excludes these two reserved addresses.
To determine the usable host range for a /26 subnet, you identify the subnet block containing the given IP. The blocks increment by 64 in the last octet: 0-63, 64-127, 128-191, and 192-255. Since 172.16.20.190 falls within 128-191, the network address is 172.16.20.128 and the broadcast address is 172.16.20.191. Usable hosts are all addresses between these two, from 172.16.20.129 to 172.16.20.190.
A common exam trap is confusing the network and broadcast addresses with usable hosts. Including the network (.128) or broadcast (.191) addresses as usable leads to incorrect answers. Practically, Cisco devices never assign these reserved addresses to hosts. Understanding subnet boundaries and reserved addresses is critical for accurate subnetting and IP planning in CCNA scenarios.
KKey Concepts to Remember
A /26 subnet mask divides an IP network into blocks of 64 addresses, including network and broadcast addresses.
The network address is the first IP in the subnet block and cannot be assigned to hosts.
The broadcast address is the last IP in the subnet block and is reserved for network-wide communication.
Usable host addresses are all IPs between the network and broadcast addresses within the subnet block.
Subnet blocks increment by the number of host addresses per subnet, which is 64 for a /26 mask.
Correct subnetting requires excluding reserved network and broadcast addresses from usable host ranges.
Misidentifying subnet boundaries or including reserved addresses leads to common exam mistakes.
Cisco devices never assign network or broadcast addresses to hosts, reinforcing the importance of correct subnetting.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
A /26 subnet mask divides an IP network into blocks of 64 addresses, including network and broadcast addresses.
Real-world example
How this comes up in practice
A network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
Review a /26 subnet mask divides an IP network into blocks of 64 addresses, including network and broadcast addresses., then practise related 200-301 questions on the same topic to reinforce the concept.
Network Infrastructure and Connectivity — This question tests Network Infrastructure and Connectivity — A /26 subnet mask divides an IP network into blocks of 64 addresses, including network and broadcast addresses..
What is the correct answer to this question?
The correct answer is: 172.16.20.129 to 172.16.20.190 — A /26 uses blocks of 64 addresses. In practical terms, the fourth-octet ranges are 0–63, 64–127, 128–191, and 192–255. Since 190 falls inside the 128–191 block, the network address is .128 and the broadcast address is .191. That leaves .129 through .190 as the usable range.
This is a strong test of whether you can identify the correct block and then exclude the reserved boundary addresses correctly.
What should I do if I get this 200-301 question wrong?
Review a /26 subnet mask divides an IP network into blocks of 64 addresses, including network and broadcast addresses., then practise related 200-301 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
A /26 subnet mask divides an IP network into blocks of 64 addresses, including network and broadcast addresses.
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