A router works at which layer of the OSI reference model?
- A.Physical layer
- B.Data Link layer
- C.Network layer
- D.Transport layer
Correct answer
Explanation
The correct answer is C, Network layer. A router joins two or more different networks and decides, for every packet, which outgoing line will carry it towards its destination. It makes that decision by reading the destination IP address, and the IP address is a network layer address, which is the third layer of the OSI model counting from the bottom. Option A is wrong because devices of the physical layer, such as a repeater or a hub, only pass on or regenerate electrical signals and cannot read any address. Option B is wrong because data link layer devices, namely the switch and the bridge, forward frames using MAC addresses and work within one network rather than between networks. Option D is wrong because the transport layer is where TCP and UDP break data into segments and manage acknowledgements; a gateway may operate up to that level and above, but an ordinary router does not.
Read the full article: Computer Networks: Topologies, Devices and OSI Layers
Practice Questions
View allIn terms of computers, the set of ways in which an adversary can enter a system and can potentially cause damage is called:
- A.Attack Surface
- B.Attack Signature
- C.Attack Pattern
- D.Attack Path
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The attack surface of a system is the total collection of every point at which an unauthorised person could try to enter it or pull data out of it: open ports, running services, user accounts, login pages, removable drives and even the employees who can be tricked.
Read the full explanation →Which of the following devices performs signal conversion?
- A.Modulator
- B.Mouse
- C.Plotter
- D.Keyboard
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A modulator changes the form of a signal: it loads the digital bits produced by a computer onto an analog carrier wave so that they can travel over a telephone line, a cable or a radio link.
Read the full explanation →What is the full form of GPRS in mobile computing?
- A.General Packet Radio Service
- B.General Packet Route service
- C.General Package Radio Service
- D.General Packet Radiation Service
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GPRS was added to the 2G cellular system so that the same radio channel could carry data in packets instead of holding a circuit open the way a voice call does.
Read the full explanation →In which network topology is every node connected to a single central device?
- A.Bus topology
- B.Ring topology
- C.Star topology
- D.Mesh topology
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In a star network every computer has its own cable running to a central hub or switch, so the shape resembles the spokes of a wheel.
Read the full explanation →How many cables are needed to connect 6 computers in a fully connected mesh topology?
- A.12
- B.15
- C.18
- D.30
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In a full mesh every node is joined directly to every other node, so the number of links equals the number of pairs that can be formed from the nodes, given by the formula n(n-1)/2.
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