Cisco CCNA mock exam questions sample test – Question 88

.Examine the diagram below and assume that routing is configured properly.
Why is Host A unable to ping Host B?

A. The IP address of Switch A is incorrect
B. The gateway address of Host B is incorrect
C. The IP address of Host A is incorrect
D. The Fa0/2 and Fa0/1 interfaces on R1 and R2 are not in the same subnet

Correct Answer: C

Explanation:
The IP address of Host A is incorrect. The Fa0/1 interface on R1 (Host A’s default gateway) is in the 192.168.1.64/27 network, and Host A’s IP address is in the 192.168.1.32/27
network. With a 27-bit mask against the 192.168.1.0 classful network, the resulting subnets are:
192.168.1.0
192.168.1.32
192.168.1.64
192.168.1.92
And so it would continue, increasing the fourth octet in intervals of 32. By only going this far we can see that they are in different subnets.
The IP address of Switch A is correct for its subnet because it needs to be in the same subnet as the Fa0/1 interface on R1. Even if it were incorrect or missing altogether it would
have no impact on Host A. Switches merely switch frames based on MAC addresses and only need an IP address for management purposes.
The gateway address of Host B is correct. It is in the same subnet (15.0.0.0/8) with the Fa0/2 interface on R2, its gateway.
The Fa0/2 and Fa0/1 interfaces on R1 and R2 are in the same subnet. Using a 25-bit mask against the 192.18.5.0/24 classful network yields the following subnets:
192.18.5.0
192.168.5.128
Both router interfaces in question are in the 192.18.5.0 subnet.
Objective:
Network Fundamentals
Sub-Objective:
Configure, verify, and troubleshoot IPv4 addressing and subnetting
References:
Cisco > Support > IP Routing > Design TechNotes > Document ID: 13788 > IP Addressing and Subnetting for New Users