CCNA – Troubleshooting

Question 1

Explanation

The subnet of Fa0/0 of R2 is 172.16.109.0/26 (range from 172.16.109.0 to 172.16.109.63) which covers the subnet of S0/1 interface 172.16.109.4/30 so in fact the answer C is not correct. But from the output of the “show ip interface brief” command we see both Fa0/0 and S0/1 interfaces’ statuses are ‘up/up’ -> they are working normally. So we think there is a typo in the subnet mask of Fa0/0. It should not be ‘/26’ but longer one, ‘/28’, for example. So you should still choose answer C in this question.

Question 2

Explanation

The “Operational Mode” is “static access” so this port is currently in access mode.

Question 3

Explanation

Both routers must use the same password for CHAP to authentication.

Question 4

Explanation

From the output we see the Serial0/0 of RouterA is in “status up/protocol down” state which indicates a Layer 2 problem so the problem can be:

+ Keepalives mismatch
+ Encapsulation mismatch
+ Clocking problem

Question 5

Question 6

Question 7

Explanation

Now let’s find out the range of the networks on serial link:

For the network 192.168.1.62/27:

Increment: 32
Network address: 192.168.1.32
Broadcast address: 192.168.1.63

For the network 192.168.1.65/27:

Increment: 32
Network address: 192.168.1.64
Broadcast address: 192.168.1.95

-> These two IP addresses don’t belong to the same network and they can’t see each other -> D is the correct answer.

Question 8

Question 9

Explanation

The “System Configuration Dialog” appears only when no startup configuration file is found. The network administrator has made a mistake because the command “copy startup-config running-config” will copy the startup config (which is empty) over the running config (which is configured by the administrator). So everything configured was deleted.

Note: We can tell the router to ignore the start-up configuration on the next reload by setting the register to 0×2142. This will make the “System Configuration Dialog” appear at the next reload.