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hardmultiple choiceObjective-mapped

Which prefix length corresponds to the subnet mask 255.255.255.192?

Answer choices

Why each option matters

Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.

A

Distractor review

/25

This is wrong because /25 corresponds to 255.255.255.128.

B

Best answer

/26

This is correct because 255.255.255.192 equals 26 network bits.

C

Distractor review

/27

This is wrong because /27 corresponds to 255.255.255.224.

D

Distractor review

/28

This is wrong because /28 corresponds to 255.255.255.240.

Common exam trap

Common exam trap: answer the scenario, not the keyword

A frequent exam trap is mistaking the subnet mask 255.255.255.192 for 255.255.255.128 or 255.255.255.224. Candidates often confuse /26 with /25 or /27 because these masks differ by only one or two bits in the last octet. This confusion leads to incorrect subnetting calculations, such as wrong host counts or subnet ranges. The trap arises because the decimal values 128, 192, and 224 are close and represent different binary patterns. Misreading these can cause errors in ACL design or routing decisions, which are critical in Cisco network configurations.

Technical deep dive

How to think about this question

Subnetting is a fundamental networking concept that divides a larger IP network into smaller, manageable subnetworks. The subnet mask determines which portion of an IP address represents the network and which part represents the host. In IPv4, subnet masks are often expressed in dotted decimal notation or as prefix lengths (CIDR notation), where the prefix length indicates the number of bits set to 1 in the subnet mask. The subnet mask 255.255.255.192 translates to a binary mask of 11111111.11111111.11111111.11000000. This means the first 26 bits are network bits, and the remaining 6 bits are available for host addressing. Therefore, the prefix length is /26. Cisco devices and CCNA exam questions expect you to quickly convert between dotted decimal masks and prefix lengths to understand subnet boundaries, calculate host ranges, and configure routing or ACLs correctly. A common exam trap is confusing the subnet mask 255.255.255.192 with similar masks like 255.255.255.128 (/25) or 255.255.255.224 (/27). These masks differ by how many bits are allocated to the network portion, which directly affects the number of hosts per subnet. Misidentifying the prefix length can lead to incorrect subnetting, routing errors, or ACL misconfigurations in Cisco environments. Practically, understanding this conversion helps in designing efficient IP schemes and troubleshooting network segmentation.

KKey Concepts to Remember

  • Subnet masks define the boundary between network and host portions of an IP address by setting bits to 1 for network and 0 for host.
  • The prefix length notation (/26) represents the count of continuous 1 bits in the subnet mask, indicating network bits.
  • The subnet mask 255.255.255.192 corresponds to a /26 prefix because its binary form has 26 leading ones.
  • Cisco devices use prefix lengths to interpret subnet masks for routing, ACLs, and IP address management.
  • Confusing similar subnet masks like 255.255.255.128 (/25) and 255.255.255.192 (/26) leads to subnetting errors in Cisco exams.
  • Correct subnet mask identification is essential for calculating subnet sizes, host counts, and designing efficient IP schemes.
  • Subnetting skills are critical for configuring VLANs, ACLs, and routing protocols in Cisco network environments.
  • Understanding binary to decimal conversion of subnet masks improves accuracy in CCNA exam subnetting questions.

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.

Related practice questions

Related 200-301 practice-question pages

Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.

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CCNA IPv6 practice questions

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More questions from this exam

Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.

Question 1

A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?

Question 2

A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?

Question 3

What is the OSPF metric called?

Question 4

A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?

Question 5

A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?

Question 6

A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?

FAQ

Questions learners often ask

What does this 200-301 question test?

Subnet masks define the boundary between network and host portions of an IP address by setting bits to 1 for network and 0 for host.

What is the correct answer to this question?

The correct answer is: /26 — The mask 255.255.255.192 corresponds to /26. In practical terms, the first three octets contribute 24 network bits, and 192 in binary is 11000000, which contributes 2 more network bits. That totals 26 network bits. This is a standard conversion skill that matters in subnetting, ACL design, and route interpretation.

What should I do if I get this 200-301 question wrong?

Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.

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