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22 votes
22 votes

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?

  1. $3$
  2. $12$
  3. $6$
  4. $8$
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3 Answers

45 votes
45 votes

Answer C

For each interface, router has one entry in routing table. 

Each interface out of a router = 1 subnet

So, here 2 + 3 + 2 = 7 

but 1 is common (router to router) so 7 - 1 = 6

 

below image ref- https://www.cisco.com/c/en/us/support/docs/ip/routing-information-protocol-rip/13788-3.html

 

Also Please find screenshot from Kurose 

edited by
10 votes
10 votes
According to me answer should be 3 as routers performs a logical duvision based on ip and hence the each area connected to Ethernet would have one subnet each and upper portion constitute a one subnet

 

Thus the topmost router constitute a T point for subnet division which is 3
5 votes
5 votes

Thanks @  for posting the reference

After reading the explanation from Kurose and Ross, finally arrived this answer 6. This is very nice and very fundamental question in computer networks where I didn’t know the subtle notion hidden inside this fundamental question and learnt that now.

Answer:

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