Consider an enterprise network with two Ethernet segments, a web server and a firewall, connected via three routers as shown below. What is the number of subnets inside the enterprise network?
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GATE CSE 2022 · Q22
MCQ1 markEasy
Time
Consider an enterprise network with two Ethernet segments, a web server and a firewall, connected via three routers as shown below. What is the number of subnets inside the enterprise network?
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Solution
Step-by-step verified solution
Official answer: C) 6
IPv4, CIDR and NATA subnet (or broadcast domain/network segment) is an isolated network partition separated by router interfaces or firewalls. Each network interface on a router connects to a distinct subnet.
Inside the enterprise network shown in the diagram, we can count each distinct network segment:
Left Ethernet segment: connects the left hosts to the left router (1 subnet).
Right Ethernet segment: connects the right hosts to the right router (1 subnet).
Web server segment: connects the web server to the top router (1 subnet).
Link between Left Router and Top Router: a point-to-point link forming a subnet (1 subnet).
Link between Top Router and Right Router: a point-to-point link forming a subnet (1 subnet).
Link between Firewall and Left Router: the internal connection inside the enterprise boundary (1 subnet).
Adding these up gives:
Thus, there are 6 subnets inside the enterprise network, corresponding to option (C).
Try the question first, then check your work.
Examiner trap
The misconception this question tests
Count every distinct broadcast domain (network segment): each LAN, each point-to-point link between routers, and the links to the server and firewall.
This IPv4, CIDR and NAT previous year question is Q22 of the GATE CSE 2022 paper. Find more GATE CSE PYQs on IPv4, CIDR and NAT in Computer Networks, or browse all GATE CSE PYQs.
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IPv4, CIDR and NAT in GATE CSE
IPv4, CIDR and NAT has 14 GATE CSE PYQs across 10 papers from 2012 to 2025. 5 of them are 1-mark MCQs like this one, and it is the only one in GATE CSE 2022.
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Independent practice explanation verified by the GateAI team. GATE is conducted by the IITs; question text follows the official paper.