You have established a console session with R1 and you are attempting to download an IOS image from the
TFTP server in the diagram below.
However, you are unable to make the connection to 150.140.6.5. What is the problem?
A.
The IP address of the management station is incorrect
B.
The IP address of the TFTP server is incorrect
C.
The interfaces between R1and R2 are not in the same subnet
D.
The IP address of Switch B is incorrect
Explanation:
The IP address of the TFTP server is incorrect. The TFTP server, Switch B and the Fa0/2 interface on R3
should all be in the same subnet. With a 27-bit mask (255.255.255.224) against the 150.140.0.0 classful
network the resulting subnets are:
150.140.0.0
150.140.0.32
150.140.0.64
and so on, incrementing in intervals of 32 in the last octet until it reaches the 150.140.6.0 subnet.
150.140.6.0
150.140.6.32
150.140.6.64
At this point, we can see that Switch B and the router interface are in the 150.140.6.32 subnet, while the TFTP
server is in the 150.140.6.0 subnet. The IP address of the TFTP server needs to be in the 150.140.6.33-
150.140.6.62 range, while avoiding the addresses already used on R1 and the switch.
The IP address of the management station does not appear to be in any of the networks listed in the diagram,
but that doesn’t matter since the connection to the router is through the console cable which does not require a
correct IP address.
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.
As we have already determined, the IP address of Switch B is correct. Even if it were incorrect or missing
altogether, it would have no impact on connecting to the TFTP server. Switches merely switch frames based on
MAC addresses and only need an IP address for management purposes.
Objective:
Routing Fundamentals
Sub-Objective:
Troubleshoot basic Layer 3 end-to-end connectivity issuesCisco > Support > IP Routing > Design TechNotes > Document ID: 13788 > IP Addressing and Subnetting for
New Users