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CCST Networking (100-150). Set it up and run it.
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wrong one is wrong; Simulation puts a clock on it and chooses each question from
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The five questions
1. Refer to the exhibit. A technician reviews four candidate host addresses in a planning table. Which listed address is invalid because an octet is out of range?
- A. Address A
- B. Address C
- C. Address B
- D. Address D
Correct answer: B.
Address C, 172.16.9.260, has a final octet of 260, which exceeds the maximum octet value of 255. An octet must be 0 to 255, so this address is invalid and cannot be assigned.
Why the others are wrong. Address A (192.168.10.40), Address B (10.20.30.40), and Address D (192.168.10.75) each keep all four octets within the legal 0 to 255 range, so all three are correctly formed and usable IPv4 host addresses, unlike the out-of-range Address C.
2. Refer to the exhibit. A frame arrives on Gi0/3 from a new host, addressed to destination MAC 0050.7966.6802. What are the switch's two actions? (Choose two.)
- A. Flood the frame out every port including Gi0/3
- B. Learn the new source MAC on port Gi0/3
- C. Forward the frame out Gi0/2 to the destination
- D. Route the frame to another IP subnet
- E. Discard the frame because the source is unknown
Correct answer: B.
The switch learns the new source MAC and maps it to Gi0/3, and because the destination MAC 0050.7966.6802 is already in the table on Gi0/2, it forwards the frame out only Gi0/2 rather than flooding it.
Why the others are wrong. It does not flood, because the destination is a known entry, and it never includes the arrival port when it does flood. It does not route to another subnet, which is a Layer 3 function. It does not discard the frame; an unknown source is simply learned, not dropped.
3. In the seven-layer OSI reference model, the layers are numbered from bottom to top. Which layer is layer 3, responsible for logical addressing and routing?
- A. Network
- B. Physical
- C. Data Link
- D. Transport
Correct answer: A.
The OSI model is numbered from the bottom upward: Physical is layer 1, Data Link is layer 2, and Network is layer 3, where logical IP addressing and routing between different networks take place.
Why the others are wrong. Physical, layer 1, moves raw bits over the medium and does no addressing. Data Link, layer 2, uses MAC addresses to move frames within one link. Transport, layer 4, handles segmentation and end-to-end delivery, not path selection between networks.
4. An IPv4 address such as 192.168.10.25 is written as four decimal numbers separated by dots. How many bits are in a complete IPv4 address?
- A. 48 bits
- B. 64 bits
- C. 128 bits
- D. 32 bits
Correct answer: D.
An IPv4 address is 32 bits long, divided into four 8-bit octets. Each octet is written in decimal from 0 to 255, giving the familiar dotted-decimal form such as 192.168.10.25.
Why the others are wrong. 48 bits is the length of an Ethernet MAC address, not an IPv4 address. 128 bits is the length of an IPv6 address, which replaces IPv4 with a much larger space. 64 bits matches neither addressing scheme and is simply incorrect for IPv4.
5. A device on the network stores files and runs applications that many users connect to and request services from. What type of endpoint is this?
- A. A laptop
- B. An IP phone
- C. A network switch
- D. A server
Correct answer: D.
A server is an endpoint dedicated to providing resources, such as files, applications, web pages, or authentication, that client devices across the network request and consume.
Why the others are wrong. A laptop is a client endpoint that consumes services rather than hosting them for many users. An IP phone is an endpoint for voice calls, not a general resource host. A network switch is an intermediary device that forwards frames between endpoints and does not store files or run user applications.
6. A small office needs one device to connect several wired computers into a single LAN and forward each frame only toward its destination. Which device fits?
- A. Firewall
- B. Modem
- C. Switch
- D. Repeater
Correct answer: C.
A switch builds a LAN of wired hosts and, using its MAC address table, forwards each frame out only the port leading to the destination, rather than flooding every port on the network.
Why the others are wrong. A firewall filters traffic between networks by security policy, not build a wired LAN. A modem converts signals for the ISP connection and performs no local frame switching. A repeater only regenerates a signal to extend cable distance and makes no per-port forwarding decision.
7. A help desk technician begins a network problem by asking the user what changed and what they were doing when the connection failed. Which troubleshooting step is this?
- A. Verifying full system functionality
- B. Escalating the issue to engineering
- C. Gathering information about the problem
- D. Documenting the final resolution
Correct answer: C.
Structured troubleshooting begins by gathering information, which means questioning the user, noting symptoms, and learning what recently changed, because an accurate description of the problem guides every later step and prevents chasing the wrong cause.
Why the others are wrong. Verifying full functionality happens at the end, after a fix is applied, not at the start. Escalating to engineering comes only once front-line steps fail to isolate the fault. Documenting the resolution is the closing step after the issue is confirmed fixed, not the opening question to the user.
8. A network switch forwards traffic based on MAC addresses within a local segment. At which layer of the OSI model does a traditional switch primarily operate?
- A. Layer 2, Data Link
- B. Layer 1, Physical
- C. Layer 3, Network
- D. Layer 4, Transport
Correct answer: A.
A traditional switch reads the destination MAC address in each frame and forwards it out the correct port, which is a Data Link, layer 2, function performed within a single local segment.
Why the others are wrong. Layer 1, the Physical layer, only transmits bits and cannot read addresses. Layer 3, the Network layer, is where routers forward based on IP addresses. Layer 4, the Transport layer, manages ports and reliable delivery, none of which a basic switch performs.
