SSC CGL Computer – Networking – Devices, Topologies & Protocols – Level 2 · Exam Level · Section III pace

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SSC CGL Computer – Networking – Devices, Topologies & Protocols – Level 2 · Exam Level · Section III pace – 15 questions, subject: Computer Knowledge. Every question has the correct answer with a one-line explanation; tap "Show Answer". Free practice for TNPSC, UPSC, SSC, Bank and RRB exams – Shanmugam IAS Academy, Coimbatore.

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1.  
Match the followingMatch the device with the OSI layer at which it mainly works:
P. Hub Q. Switch R. Router
1. Layer 3 – Network 2. Layer 1 – Physical 3. Layer 2 – Data Link

Correct Answer: B [P-2, Q-3, R-1]

Explanation:

Hub L1 · switch L2 · router L3 (What Does It Read?).

2.  
In a full mesh of 11 computers, how many ports does each computer need for the mesh links?

Correct Answer: C [10]

Explanation:

Each device links to every other one: n − 1 = 10 ports (55 is the number of cables).

3.  
The IPv4 address 224.0.0.9 belongs to which class?

Correct Answer: D [Class D]

Explanation:

First number 224 is in 224–239 → Class D (multicast).

4.  
Statement-basedWhich of the following is/are correct?
I. A switch forwards a frame only to the port of the destination MAC address.
II. A router works mainly at the Data Link layer.

Correct Answer: A [Only I]

Explanation:

Switch – L2, by MAC; a router is a Network-layer (L3) device.

5.  
Assertion–Reason
A: TCP is used for downloading files and e-mail.
R: TCP acknowledges data, re-sends lost segments and keeps them in order.

Correct Answer: C [Both A and R are true and R explains A]

Explanation:

Files and mail must arrive complete – TCP's reliability is the reason.

6.  
What is the data unit at the Network layer (Layer 3) called?

Correct Answer: A [packet]

Explanation:

Bits Fly, Packets Sail: bit L1 · frame L2 · packet L3 · segment L4.

7.  
Reverse questionA protocol uses well-known port 110 to download mail to one device. Name it.

Correct Answer: B [POP3]

Explanation:

POP3 110 downloads; IMAP 143 keeps mail on the server; SMTP 25 sends; FTP 20/21.

8.  
Odd one outOdd one out (by OSI layer):

Correct Answer: D [Router]

Explanation:

Hub, repeater and modem are Layer 1; the router is Layer 3.

9.  
Two-quantity comparison
Quantity I: ports needed on each device in a full mesh of 9 devices
Quantity II: cables needed in a ring of 8 devices

Correct Answer: C [Quantity I = Quantity II]

Explanation:

QI = n − 1 = 8; QII = n = 8 → equal.

10.  
How many bits long is a MAC address?

Correct Answer: A [48]

Explanation:

Answer: 48. 12 hex digits × 4 bits = 48.

11.  
Which protocol gives IP addresses to computers automatically when they join a network?

Correct Answer: C [DHCP]

Explanation:

DHCP = Dynamic Host Configuration Protocol.

12.  
Trick SpotterFor the mask 255.255.255.248, how many host bits are left and how many usable hosts does that give?

Correct Answer: B [3 bits, 6 hosts]

Explanation:

248 = 11111000 leaves 3 host bits: 2³ − 2 = 6 (network and broadcast addresses reserved).

13.  
Which OSI layer lies directly between the Network layer and the Session layer?

Correct Answer: D [Transport]

Explanation:

1 Physical · 2 Data Link · 3 Network · 4 Transport · 5 Session.

14.  
Which of these is a private IPv4 address (not routed on the Internet)?

Correct Answer: C [192.168.5.20]

Explanation:

Private ranges: 10.x, 172.16–31.x, 192.168.x.

15.  
On a video call, two friends speak and hear each other at the same time. This transmission mode is:

Correct Answer: D [Full duplex]

Explanation:

Both directions at the same time = full duplex.

➤ Full notes, shortcuts and every answer explained – SSC CGL 2026 Computer Knowledge book (₹149): www.shanmugamiasacademy.in/study-materials/ssc-cgl-computer-knowledge

📘 SSC CGL 2026 – Computer Knowledge (Tier II Paper I – Section III)
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