2. CCNA® INTERVIEW QUESTIONS
100 Interview Questions and Answers based on CCNA® concepts
Includes Topology and Scenario based Questions and Answers
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3. Preface
The CCNA® certification is one of the most reputed and respected courses in the
computer networking industry. This EBook is ideal for candidates who have
completed or pursing CCNA® certification and intending to go for an interview,
which requires the CCNA® certification. The questions in the EBook would help
you to perform a self assessment of the concepts learnt during the CCNA® course
and how well you have understood the same. Scenario and topology based
questions with answers are also included in the eBook.

4. Sample Questions provided below with answers and explanation
Question 1
In the above diagram, three computers with IP address 192.168.1.2 , 192.168.1.3
and 192.168.2.1 is connected to a layer 2 switch. Can the computer with IP address
192.168.1.2, ping the computer with IP address 192.168.2.1?
Explanation
The computer with IP address 192.168.1.2, belongs to the network address of
192.168.1.0. The computer with IP address 192.168.2.1 belongs to the network
address of 192.168.2.0. Since both the computers belong to different network
addresses, communication between them is possible only if a layer 3 device or a
router is required. Computers require the mac-address of the peer for sending out
the packet. ARP is used on an ethernet segment to find out the mac-address of the
peer. ARP can be used to find out the mac-addresses of devices belonging to the
same network address. If the destination is on a different network address, the ARP
request is sent to the gateway. So in this case, there is no gateway configured.

5. Question 2
In the above diagram, the computer with IP address 192.168.1.2 pings the router
with IP address 192.168.1.1. Explain how the packet is processed by the router and
whether routing is involved in the scenario.
Explanation
The computer constructs the IP header with source IP address as 192.168.1.2 and
destination IP address as 192.168.1.3. The IP header would be encapsulated in an
ethernet frame with source mac-address as that of the computer’s mac-address and
destination mac-address as the router’s mac-address. When the frame reaches the
router, the router looks into the destination mac-address of the frame. On a match,
the FCS value of the frame is calculated and verified. The router then looks into
the destination IP address of the IP header. Since the IP address is intended for
itself, the router prepares a response. There is no routing involved since the
destination IP address is on the same physical segment.

6. Question 3
Two interfaces of a router is configured with IP addresses 192.168.1.1, subnet
mask 255.255.255.0 and IP address 192.168.2.1, subnet mask 255.255.255.0.
Would the routing table of the router contain any information?
Explanation
When the interfaces are configured with the respective IP addresses and subnet
mask, the router would perform an ANding operation with the IP address and
subnet mask. This would ultimately yield the network address for the interface.
Once the interfaces are configured with the IP addresses and subnet masks, two
entries would be available in the routing tables which are 192.168.1.0 (Network
address of 192.168.1.1) and 192.168.2.0 (Network address of 192.168.2.1), which
would be listed as directly connected networks.
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