CCNA FAQ: Introduction to TCP/IP
Q1. What must happen if a DHCP IP conflict occurs?
A. Proxy ARP will fix the issue.
B. The client uses a gratuitous ARP to fix the issue.
C. The administrator must fix the conflict by hand at the DHCP server.
D. The DHCP server will reassign new IP addresses to both computers.
Answer: C. If a DHCP conflct is detected, either by the server sending a ping and getting a response or by a host using a gratuitous ARP (arp’ing for its own IP address and seeing if a host responds), then the server will hold that address and not use it again until it is fied by an administrator.
Q2. Which of the following Application layer protocols sets up a secure session that’s similar to Telnet?
Answer: B. Secure Shell (SSH) protocol sets up a secure session that’s similar to Telnet over a standard TCP/IP connection and is employed for doing things like logging into systems, running programs on remote systems, and moving fies from one system to another.
Q3. Which of the following mechanisms is used by the client to avoid a duplicate IP address during the DHCP process?
C. gratuitous arp
Answer: C. A host uses something called a gratuitous ARP to help avoid a possible duplicate address. The DHCP client sends an ARP broadcast out on the local LAN or VLAN using its newly assigned address to solve conflcts before they occur.
Q4. What protocol is used to find the hardware address of a local device?
Answer: B. Address Resolution Protocol (ARP) is used to fid the hardware address from a known IP address.
Q5. Which of the following are layers in the TCP/IP model? (Choose three.)
E. Data Link
Answer: A, C, D. The listed answers are from the OSI model and the question asked about the TCP/IP protocol stack (DoD model). Yes, it is normal for the objectives to have this type of question. However, let’s just look for what is wrong. First, the Session layer is not in the TCP/IP model; neither are the Data Link and Physical layers. This leaves us with the Transport layer (Host-to-host in the DoD model), Internet layer (Network layer in the OSI), and Application layer (Application/Process in the DoD). Remember, the CCENT objectives can list the layers as OSI layers or DoD layer at any time, regardless of what the question is asking.
Q6. Which class of IP address provides a maximum of only 254 host addresses per network ID?
A. Class A
B. Class B
C. Class C
D. Class D
E. Class E
Answer: C. A Class C network address has only 8 bits for defiing hosts: 28 – 2 = 256.
Q7. Which of the following describe the DHCP Discover message? (Choose two.)
A. It uses FF:FF:FF:FF:FF:FF as a layer 2 broadcast.
B. It uses UDP as the Transport layer protocol.
C. It uses TCP as the Transport layer protocol.
D. It does not use a layer 2 destination address.
Answer: A, B. A client that sends out a DHCP Discover message in order to receive an IP address sends out a broadcast at both layer 2 and layer 3. The layer 2 broadcast is all Fs in hex, or FF:FF:FF:FF:FF:FF. The layer 3 broadcast is 255.255.255.255, which means any networks and all hosts. DHCP is connectionless, which means it uses User Datagram Protocol (UDP) at the Transport layer, also called the Host-to-host layer.
Q8. Which layer 4 protocol is used for a Telnet connection?
Answer: B. Although Telnet does use TCP and IP (TCP/IP), the question specifially asks about layer 4, and IP works at layer 3. Telnet uses TCP at layer 4.
Q9. Private IP addressing was specified in RFC __________.
Answer: RFC 1918 These addresses can be used on a private network, but they’re not routable through the Internet.
Q10. Which of the following services use TCP? (Choose three.)
Answer: B, D, E. SMTP, FTP, and HTTP use TCP.
Q11. Which Class of IP addresses uses the pattern shown below?
A. Class A
B. Class B
C. Class C
D. Class D
Answer: C. Class C addresses devote 24 bits to the network portion and 8 bits to the host portion.
Q12. Which of the following is an example of a multicast address?
Answer: C. The range of multicast addresses starts with 188.8.131.52 and goes through 184.108.40.206.
Q13. The following illustration shows a data structure header. What protocol is this header from?
Answer: C. First, you should know easily that only TCP and UDP work at the Transport layer, so now you have a 50/50 shot. However, since the header has sequencing, acknowledgment, and window numbers, the answer can only be TCP.
Q14. If you use either Telnet or FTP, what layer are you using to generate the data?
Answer: A. Both FTP and Telnet use TCP at the Transport layer; however, they both are Application layer protocols, so the Application layer is the best answer for this question.
Q15. The DoD model (also called the TCP/IP stack) has four layers. Which layer of the DoD model is equivalent to the Network layer of the OSI model?
D. Network Access
Answer: C. The four layers of the DoD model are Application/Process, Host-to-Host, Internet, and Network Access. The Internet layer is equivalent to the Network layer of the OSI model.
Q16. Which two of the following are private IP addresses?
Answer: C, E. The Class A private address range is 10.0.0.0 through 10.255.255.255. The Class B private address range is 172.16.0.0 through 172.31.255.255, and the Class C private address range is 192.168.0.0 through 192.168.255.255.
Q17. What layer in the TCP/IP stack is equivalent to the Transport layer of the OSI model?
D. Network Access
Answer: B. The four layers of the TCP/IP stack (also called the DoD model) are Application/ Process, Host-to-host, Internet, and Network Access. The Host-to-host layer is equivalent to the Transport layer of the OSI model.
Q18. Which statements are true regarding ICMP packets? (Choose two).
A. ICMP guarantees datagram delivery.
B. ICMP can provide hosts with information about network problems.
C. ICMP is encapsulated within IP datagrams.
D. ICMP is encapsulated within UDP datagrams.
Answer: B, C. ICMP is used for diagnostics and destination unreachable messages. ICMP is encapsulated within IP datagrams, and because it is used for diagnostics, it will provide hosts with information about network problems.
Q19. What is the address range of a Class B network address in binary?
Answer: C. The range of a Class B network address is 128–191. This makes our binary range 10xxxxxx.
Q20. Drag the steps in the DHCP process and place them in the correct order on the right.
left list: right list:
DHCPOffer Drop Target A
DHCPDiscover Drop Target B
DHCPAck Drop Target C
DHCPRequest Drop Target D
CCNA Frequently Asked Questions CCNA Exam Questions with Explanation