GATE CSE 2019 | Question: 49

Question

Consider that $15$ machines need to be connected in a LAN using $8$-port Ethernet switches. Assume that these switches do not have any separate uplink ports. The minimum number of switches needed is ______

Comments

What is meant by :-

 “switches do not have any separate uplink ports” ?

Edit: Found the answer to the question:-

When a device, such as a switch, is said to not have any separate uplink ports, it means that it does not have any ports that are specifically designated for connecting to other devices, such as routers. Instead, all of the ports on the device can be used to connect to other devices or devices can be daisy chained together using one of the device's ports.

 In networking, an uplink port is a port that is used to connect one device to another device at a higher level in the network hierarchy. For example, an uplink port on a switch might be used to connect the switch to a router, while an uplink port on a router might be used to connect the router to a broadband modem. Uplink ports are typically used to expand the capabilities of a network by adding additional devices or to connect a network to the internet.

Ref: Networking ALL-IN-ONE 7th Edition by Doug Lowe, Uplink Port vs Normal Port on Network Switch

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GREAT EXPLAINATION THANKS ALOT @Abhrajyoti00 FOR CLEAR THE QUESTION.

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@Abhrajyoti00 Just looking Like Waw…..

Answer 1

Out of 8 ports 1 port dedicated to the switch itself .hence 7 available ports for the clients.there are 15 clients s no of switches =3

Answer 2

In LAN all the machines are interconnected. If we use a switch for 8 machines, and another for 7 machines; the first 8 machines won't be connected to the latter 7. So using two switches won't be enough.

In the first switch A,

• First 7 ports — 7 machines.
• Last port — Connect to other switch B.

In the second switch B

• One port already connected to A
• 6 ports — 6 machines
• Last port — Connect to other switch C.

In the third switch C

• One port already connected to B
• 2 ports — 2 machines.

Done! We need 3 switches.

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Alternatively.

Machines to be connected = 15.

Ports available per switch = 7 (NOT 8)

So, 15/7 = 2.142 => 3 switches are required.

Comments

Hey!

Can you please explain this to me. I am not able to get the objective of this question.