Cisco CCNA mock exam questions sample test – Question 269

.You receive the following error message after addressing and enabling an interface:
%192.168.16.0 overlaps with FastEthernet0/0
Which two are NOT the causes of the error message? (Choose two.)

A. incorrect subnet mask in the new interface
B. incorrect IP address on the new interface
C. incorrect encapsulation configured
D. failure to issue the no shutdown command


Correct Answer: CD

Explanation:
The error message %192.168.16.0 overlaps with FastEthernet0/0 indicates that the newly configured interface is in the same subnet as an existing interface. This can occur if there is
an incorrect subnet mask or an address that inadvertently places the new interface in that subnet. Each router interface must be in a different subnet to function. For example, when
the series of commands below is executed on a router, it will elicit the error message because the two IP addresses used are in the same subnet given the subnet mask in use.
Router#config t
Router(config)#interface S0
Router(config-if)#ip address 192.168.1.17 255.255.255.0
Router(config-if)#no shutdown
Router(config-if)interface S1
Router(config-if)#ip address 192.168.1.65 255.255.255.0
Router(config-if)#no shutdown
0%192.168.1.0 overlaps with Serial 0
It’s also a valuable skill to be able to recognize these problems before the router tells you about them. In the diagram below, you should be able to spot the problem with the two
planned addresses on the router as being in the same subnet before you receive the error message.
An incorrect encapsulation would prevent the interface from working, but would not generate this message.
If the no shutdown command had not been issued, we would not be receiving this error. It is only generated when an attempt is made to enable an incorrectly configured interface.
Objective:
Routing Fundamentals
Sub-Objective:
Troubleshoot basic Layer 3 end-to-end connectivity issues
References:
Cisco Documentation > Configuring IP Addressing