Correct option is C
We are given:
Computer A
- IP Address: 203.197.2.53
- Subnet Mask: 255.255.128.0
Computer B
- IP Address: 203.197.75.201
- Subnet Mask: 255.255.192.0
We must determine whether each computer considers the other to be on the same network or a different network.
Step 1: Understand the Subnet Masks
A’s Subnet Mask
255.255.128.
Binary:
11111111.11111111.10000000.00000000
This corresponds to:
/17
Meaning:
- First 17 bits = Network portion
- Remaining bits = Host portion
B’s Subnet Mask
255.255.192.0
Binary:
11111111.11111111.11000000.00000000
This corresponds to:
/18
Meaning:
- First 18 bits = Network portion
Step 2: Check A’s View of B
A uses subnet mask:
255.255.128.0
So, A checks whether B belongs to the same /17 network.
A’s Network Address
IP:
203.197.2.53
Third octet = 2
With /17:
- Network ranges are:
- 0–127
- 128–255
Since 2 lies in:
0 − 127
A’s network is:
203.197.0.0/17
B’s IP
203.197.75.201
Third octet = 75
75 also lies in:
0 − 127
Thus, B also belongs to:
203.197.0.0/17
Therefore:
Step 3: Check B’s View of A
B uses subnet mask:
255.255.192.0
i.e. /18.
With /18:
- Third octet ranges become:
- 0–63
- 64–127
- 128–191
- 192–255
B’s Network
B’s IP:
203.197.75.201
Third octet = 75
75 lies in:
64 − 127
So, B belongs to:
203.197.64.0/18
A’s IP
203.197.2.53
Third octet = 2
2 lies in:
0 − 63
So, A belongs to:
203.197.0.0/18
Thus, A and B are in different /18 networks.
Therefore:
Final Conclusion
- A thinks B is on the same network.
- B thinks A is on a different network.
Correct Answer
Information Booster
1. Subnetting Rule
Two hosts are considered on the same network if:
(IP AND Subnet Mask)
gives the same network address.
2. CIDR Notation
| Subnet Mask | CIDR |
| 255.255.128.0 | /17 |
| 255.255.192.0 | /18 |
3. Important Concept
Communication assumptions may become asymmetric when hosts use different subnet masks. One host may think the destination is local while the other thinks it is remote.
English
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