Sample/practice exam 18 December, questions and answers PDF

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CCNA3 Chapter 2 Practice Test Answers An Ethernet network is using CSMA/CD and a collision has occurred. Which host will be the next to transmit data? • • • •

The host that was the first to detect the collision. The host that was the first to transmit data that was involved in the collision. A host that has data to transmit and whose backoff period expires first. A host that has data to transmit and is holding the token at the time.

What is necessary for an Ethernet network to be free of collisions? • • • •

The network must use fibre optic cable. The network must use layer 2 switches. Hubs must be replaced with switches to reduce the number of collision domains. The network must use full duplex transmission and be fully switched.

Which frames are flooded by a switch through all ports except the incoming port? • • • •

Broadcast frames, multicast frames and frames where the destination MAC address is not in the MAC address table. Unicast frames, multicast frames and frames where the source MAC address is not in the MAC address table. Broadcast frames, multicast frames and frames where there is no known switch port that matches the source MAC address. Broadcast frames, unicast frames and frames where there is no known switch port that matches the destination MAC address.

Where does a switch get the data to build up its MAC address table? • • • •

From the destination MAC addresses of incoming frames. From the source MAC addresses of incoming frames. From the destination MAC addresses of outgoing frames. From the source MAC addresses of outgoing frames.

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How does the default behaviour of a switch differ from the default behaviour of a router when a broadcast message arrives? • • • •

There is no difference. They both forward the message through all ports except the incoming port. There is no difference. They both drop the broadcast message. The switch forwards the message through all ports except the incoming port, while the router drops it. The router forwards the message through all ports except the incoming port, while the switch drops it.

Another name for the MAC address table of a switch is the: • • • •

ARP table CAM table CAD table CDP table

How many collision domains? • • • • •

2 3 9 10 12

And how many broadcast domains? • • • • •

2 3 9 10 12

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Why are routers still required for Ethernet networks in some cases even though multilayer switches are available that operate at layer 3? • • • •

Routers operate more quickly than layer 3 switches. Routers are generally better at making connections to WANs. Switches cannot carry out routing using IP addresses. Layer 3 switches cannot split up broadcast domains.

Which is true of port based buffering but not of shared buffering in a switch? • • • •

Large frames can be accommodated more easily. Frames are linked dynamically to their exit port and sent as soon as it is available. A frame may be delayed if the frame ahead of it in the queue is waiting for its exit port to become available. Buffer memory is allocated flexibly as it is required.

Which mode of switching reads the whole frame and carries out a cyclic redundancy check? • • • •

Fast forward Cut through Fragment free Store and forward

If you type in a switch command, leave a space and then type ?, what do you get? • • • •

A list of other commands that can be typed in that mode. A list of parameters that can follow the command. An error message A repeat of the previously typed command

If you have used the up arrow key or Ctrl + P to show several previous commands from the command history, you can work back and show the later commands by pressing the down arrow key or: • • • •

Ctrl + N Ctrl + C Ctrl + D Ctrl + V

Where is the running configuration held? • • • •

Flash ROM RAM NVRAM

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Which command needs to be in a switch configuration in order for an administrator to use its web based interface? • • • •

www interface http server enable ip http server ip http activate

Which command is needed if the web based interface of a switch is to be accessed by a username and password specified in the command: userid tech password cisco. • • • •

ip http authentication aaa ip http authentication enable ip http authentication local ip http authentication tacacs

Why is it advisable to put a switch IP address on some interface other than VLAN 1? • • • •

It is not possible to put an IP address on a VLAN interface. VLAN 1 cannot be associated with a physical interface in order for messages to be sent. VLAN 99 is the only interface that allows access to the web based interface. It is more secure to use a different VLAN interface for management purposes.

Which is the correct option for configuring a switch with the address of its local router so that it can be accessed from a remote network? • • • •

SW1#default-gateway 172.16.0.1 255.255.255.0 SW1(config)# default-gateway 172.16.0.1 255.255.255.0 SW1(config-if)# default-gateway 172.16.0.1 255.255.255.0 SW1(config-line)# default-gateway 172.16.0.1 255.255.255.0

You capture a running configuration that includes the line: enable secret 5 859D23N4BA56 What will happen if you put this configuration back on a router without making any changes in this line? • • • •

All passwords will be encrypted. You will need to enter 859D23N4BA56 in order to reach privileged exec mode. The enable password must be used instead of enable secret. The router will not accept the configuration.

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You configure both a login banner and a message of the day banner on a switch. What do you see when you make a console connection to the switch? • • • •

The motd banner, then the login banner, then the prompt for a password. The login banner, then the motd banner, then the prompt for a password. The motd banner, then the prompt for a password, then the login banner. The login banner, then the prompt for a password, then the motd banner.

What is the effect of entering the commands: SW1(config)#line vty 0 15 SW1(config-line)#transport input SSH • • • •

You will not be able to Telnet to the switch. It allows you to use SSH as well as Telnet for remote access to the switch CLI. All traffic received by all switch ports will be encrypted. The switch will be able to receive SSH messages but not send them.

A port has been configured to learn a dynamic secure address. How can you ensure that this address is still known after the switch reboots? • • • •

Save the MAC address table. Reconfigure the port with a static address. Enable sticky learning then save the running configuration. Change the security violation mode.

By default, how many secure addresses can a switch port learn? • • • •

1 2 10 1024

Why do you give the command switchport mode access before setting security on a port? • • • •

The command is needed in order for any device to access the port. The default switchport mode is dynamic desirable, which does not allow security to be configured. The default switchport mode is trunk, which does not allow security to be configured. This is another way of giving the no shutdown command.

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Which type of switchport security is being configured by the command: SW1(config-if)#switchport port-security mac-address 000c.7612.3b82 • • • •

Static Dynamic Sticky Protect

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1. When a collision occurs in a network using CSMA/CD, how do hosts with data to transmit respond after the backoff period has expired? The hosts return to a listen-before-transmit mode. The hosts creating the collision have priority to send data. The hosts creating the collision retransmit the last 16 frames. The hosts extend their delay period to allow for rapid transmission. 2. Which statements correctly describe MAC addresses? (Choose three.) dynamically assigned copied into RAM during system startup layer 3 address contains a 3 byte OUI 6 bytes long 32 bits long 3. What three primary functions does data link layer encapsulation provide? (Choose three.) path determination frame delimiting addressing IP address resolution error detection port identification 4. Which of the following is a drawback of the CSMA/CD access method? Collisions can decrease network performance. It is more complex than non-deterministic protocols. Deterministic media access protocols slow network performance. CSMA/CD LAN technologies are only available at slower speeds than other LAN technologies. 5. What does the IEEE 802.2 standard represent in Ethernet technologies? MAC sublayer Physical layer Logical Link Control sublayer Network layer 6.

Refer to the exhibit. The switch and workstation are administratively configured for full-duplex operation. Which statement accurately reflects the operation of this link? No collisions will occur on this link. Only one of the devices can transmit at a time. The switch will have priority for transmitting data. The devices will default back to half duplex if excessive collisions occur. 7. Which of the following describe interframe spacing? (Choose two.) the minimum interval, measured in bit-times, that any station must wait before sending another frame the maximum interval, measured in bit-times, that any station must wait before sending another frame the 96-bit payload padding inserted into a frame to achieve a legal frame size the 96-bit frame padding transmitted between frames to achieve proper synchronization

the time allowed for slow stations to process a frame and prepare for the next frame the maximum interval within which a station must send another frame to avoid being considered unreachable 8.

9.

10.

11.

12.

13.

In the graphic, Host A has reached 50% completion in sending a 1 KB Ethernet frame to Host D when Host B wishes to transmit its own frame to Host C. What must Host B do? Host B can transmit immediately since it is connected on its own cable segment. Host B must wait to receive a CSMA transmission from the hub, to signal its turn. Host B must send a request signal to Host A by transmitting an interframe gap. Host B must wait until it is certain that Host A has completed sending its frame. After an Ethernet collision, when the backoff algorithm is invoked, which device has priority to transmit data? the device involved in the collision with the lowest MAC address the device involved in the collision with the lowest IP address any device in the collision domain whose backoff timer expires first those that began transmitting at the same time What are three functions of the upper data link sublayer in the OSI model? (Choose three.) insulates network layer protocols from changes in physical equipment identifies the network layer protocol recognizes streams of bits makes the connection with the upper layers determines the source of a transmission when multiple devices are transmitting identifies the source and destination applications Ethernet operates at which layers of the OSI model? (Choose two.) Network layer Transport layer Physical layer Application layer Session layer Data-link layer Which two features make switches preferable to hubs in Ethernet-based networks? (Choose two.) reduction in cross-talk minimizing of collisions support for UTP cabling division into broadcast domains increase in the throughput of communications Convert the binary number 10111010 into its hexadecimal equivalent. Select the correct answer from the list below. 90 BA B3

1C A1 85 14. Host A has an IP address of 172.16.225.93, a mask of 255.255.248.0, and a default gateway of 172.16.224.1. Host A needs to send a packet to a new host whose IP is 172.16.231.78. Host A performs the ANDing operation on its address and subnet mask. What two things will occur? (Choose two.) Host A will get a result of 172.16.224.0 from the AND process. Host A will send on to the media a broadcast frame that contains the packet. Host A will broadcast an ARP request for the MAC of the host 172.16.231.78. Host A will change the destination IP of the packet to 172.16.224.1 and forward the packet. Host A will encapsulate the packet in a frame with a destination MAC that is the MAC address associated with 172.16.224.1. 15. Why do hosts on an Ethernet segment that experience a collision use a random delay before attempting to transmit a frame? A random delay is used to ensure a collision-free link. A random delay value for each device is assigned by the manufacturer. A standard delay value could not be agreed upon among networking device vendors. A random delay helps prevent the stations from experiencing another collision during the transmission. 16.

Refer to the exhibit. Which option correctly identifies content that the frame data field may contain? preamble and stop frame network layer packet physical addressing FCS and SoF 17. Ethernet operates at which layer of the TCP/IP network model? application physical transport internet data link network access 18. What are the two most commonly used media types in Ethernet networks today? (Choose two.) coaxial thicknet copper twisted pair coaxial thinnet optical fiber shielded coaxial cable

19.

Refer to the exhibit. Host_A is attempting to contact Server_B. Which statements correctly describe the addressing Host_A will generate in the process? (Choose two.) A packet with the destination IP of Router_B. A frame with the destination MAC address of Switch_A. A packet with the destination IP of Router_A. A frame with the destination MAC address of Router_A. A packet with the destination IP of Server_B. A frame with the destination MAC address of Server_B. 20. What is the primary purpose of ARP? translate URLs to IP addresses resolve IPv4 addresses to MAC addresses provide dynamic IP configuration to network devices convert internal private addresses to external public addresses

CHAPTER 13

Local Area Networks: Ethernet Solutions to Odd-Numbered Review Questions and Exercises

Review Questions 1. The preamble is a 56-bit field that provides an alert and timing pulse. It is added to the frame at the physical layer and is not formally part of the frame. SFD is a onebyte field that serves as a flag. 3. A multicast address identifies a group of stations; a broadcast address identifies all stations on the network. A unicast address identifies one of the addresses in a group. 5. A layer-2 switch is an N-port bridge with additional sophistication that allows faster handling of packets. 7. The rates are as follows: Standard Ethernet: Fast Ethernet: Gigabit Ethernet: Ten-Gigabit Ethernet:

10 Mbps 100 Mbps 1 Gbps 10 Gbps

9. The common Fast Ethernet implementations are 100Base-TX, 100Base-FX, and 100Base-T4. 11. The common Ten-Gigabit Ethernet implementations are 10GBase-S, 10GBase-L, and 10GBase-E.

Exercises 13. The bytes are sent from left to right. However, the bits in each byte are sent from the least significant (rightmost) to the most significant (leftmost). We have shown the bits with spaces between bytes for readability, but we should remember that that bits are sent without gaps. The arrow shows the direction of movement. ←

01011000 11010100

00111100

11010010

01111010 11110110

1

2

15. The first byte in binary is 01000011. The least significant bit is 1. This means that the pattern defines a multicast address. A multicast address can be a destination address, but not a source address. Therefore, the receiver knows that there is an error, and discards the packet. 17. The maximum data size in the Standard Ethernet is 1500 bytes. The data of 1510 bytes, therefore, must be split between two frames. The standard dictates that the first frame must carry the maximum possible number of bytes (1500); the second frame then needs to carry only 10 bytes of data (it requires padding). The following shows the breakdown: Data size for the first frame: 1500 bytes Data size for the second frame: 46 bytes (with padding) 19. We can calculate the propagation time as t = (2500 m) / (200,000.000) = 12.5 μs. To get the total delay, we need to add propagation delay in the equipment (10 μs). This results in T = 22.5 μs.

Ethernet uses a ______ physical address that is imprinted on the network interface card (NIC). 6-byte You have 10 users plugged into a hub running 10Mbps half-duplex. There is a server connected to the switch running 10Mbps half-duplex as well. How much bandwidth does each host have to the server? 10 Mbps How many bytes are in Ethernet address? 6 How different computers are connected to a LAN by a cable? Interface card How many bits are there in the Ethernet address? 48 bits On an Ethernet network, this is the unit of data that is transmitted between network points. It has explicit minimum and maximum lengths and a set of required pieces of information that must appear within it. Frame _____ transmission technology (based on Ethernet) provides a data rate of 1 billion bits per second. Gigabit Ethernet A personal computer or workstation on an Ethernet network must have one of these cards. NIC This is a device that can be used to connect one Ethernet network to another nearby Ethernet network. bridge Each station on an Ethernet network has a unique _______ address imprinted on its network interface card (NIC). 48-bit The minimum frame length for 10-Mbps Ethernet is _______bytes. 64 The maximum frame length for 10-Mbps Ethernet is ________ bytes. 1518 ________ uses thick coaxial cable. 10Base5

__________ uses thin coaxial cable. 10Base2

________ uses fiber-optic cable. 10Base-F Fast Ethernet has a data rate of ________Mbps. 100 Gigabit Ethernet access methods include _______ mode. a. half-duplex b. full-duplex _____defines a protocol data unit (PDU) that is somewhat similar to that of HDLC. LLC Standard Ethernet (10-Mbps) uses _______ encoding. Manchester

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CCNP CIT Exam 642-831: LAN Technologies By Sean Odom Feb 6, 2004

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< Page 8 > Exam Prep Practice Questions Question 1 The IEEE 802 defines Ethernet as which IEEE standard? A. 802.3 B. 802.5 C. 802.11 D. 802.9 E. 802.3ae F. 802.11b Answer: A. The 802.3 IEEE standard describes Ethernet and CSMA/CD.

Question 2 What does UTP stand for? A. Unknown twisted pair B. Unusual twisted pair C. Unshielded twisted pair D. Usual token protocol Answer: C. UTP, or unshielded twisted pair, is the term used to describe Category 3, 5, 6, and 7 cabling made without shielding.

Question 3 What is the minimum frame size for an Ethernet Frame? A. 45 bytes B. 100 bytes C. 48 bytes D. 64 bytes E. 12 bytes F. 1518 bytes Answer: D. The minimum frame size for Ethernet is 64 bytes.

Question 4 Ethernet LAN technology employs which protocol to detect collisions in LAN transmissions? A. FDDI B. CSMA/CD C. CSMA D. RIP E BGP

E. BGP Answers: B. Ethernet technology employs th...