Subnetting

 Question 1
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?
 A 3 B 12 C 6 D 8
Computer-Networks       Subnetting       GATE 2022       Video-Explanation
Question 1 Explanation:
It can be seen as Non equal subneting.
Where router 2 (via Firewall) has the half of the addresses.
Router 1 (via web server) has other half which is further divided into two subnets which is web server and router 3. So total of 3 subnets possible.
 Question 2
Consider routing table of an organization’s router shown below:

Which of the following prefixes in CIDR notation can be collectively used to correctly aggregate all of the subnets in the routing table?
 A 12.20.164.0/20 B 12.20.164.0/22 C 12.20.164.0/21 D 12.20.168.0/22
Computer-Networks       Subnetting       GATE 2022       Video-Explanation
Question 2 Explanation:
Do bit wise and with the given subnet and subnets mask then compare to given choices IP address range.
 Question 3

Consider the following routing table at an IP router:

For each IP address in Group I identify the correct choice of the next hop from Group II using the entries from the routing table above.

```     Group I                 Group II
(i) 128.96.171.92        (a) Interface 0
(ii) 128.96.167.151      (b) Interface 1
(iii) 128.96.163.121     (c) R2
(iv) 128.96.165.121      (d) R3
(e) R4
```
 A i-a, ii-c, iii-e, iv-d B i-a, ii-d, iii-b, iv-e C i-b, ii-c, iii-d, iv-e D i-b, ii-c, iii-e, iv-d
Computer-Networks       Subnetting       GATE 2015 [Set-2]       Video-Explanation
Question 3 Explanation:
Do the AND operation of group I IP address with Netmask and compare the result with network number. if it match with network number, forward packet through that interface. Ex: 128.96.167.151 AND 255.255.254.0 = 128.96.166.0 Therefore packet will forward through R2.
There are 3 questions to complete.

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