GATE CS Mastery
Cheat sheets

GATE CS 2022 · Computer Networks

Question 22

MCQ1 markWrong answer: −1/3Medium (estimate)

Question

Consider an enterprise network with two Ethernet segments, a web server and a firewall, connected via three routers as shown below.

Enterprise network: the firewall connects to the Internet, to the top router and to the left router. The top router connects to the web server and to the right router. The left and right routers each connect to an Ethernet segment with several PCs.

What is the number of subnets inside the enterprise network?

Choose one option
Official answer and solution
Official answer
C
From
Official GATE 2022 answer key

Solution

Count each broadcast domain and point-to-point link between router interfaces within the enterprise network.

In IP networking, a subnet is formed by each separate broadcast domain (LAN segment or router-to-router point-to-point link):

  1. Ethernet segment 1 connected to router R1.
  2. Ethernet segment 2 connected to router R2.
  3. The point-to-point link connecting router R1 and router R2.
  4. The point-to-point link connecting router R1 and router R3.
  5. The point-to-point link connecting router R2 and router R3.
  6. The network segment connecting router R3 to the internal servers (Web Server and Firewall).

Summing these distinct segments gives 1+1+1+1+1+1=61 + 1 + 1 + 1 + 1 + 1 = 6 subnets inside the enterprise network.

Final answer

Option (C)

Common trap

Forgetting that point-to-point links between routers each constitute their own distinct subnet.

The answer is the one in the official GATE answer key. The solution is this site's own explanation.

Source

Paper
GATE 2022 Computer Science and Information Technology (CS)
Question
22 of 65
Section
Computer Science and Information Technology

Report an error in this question

GATE questions are the work of the organising institutes. This site is independent and is not affiliated with them.