DNS Zone Transfer

สวัสดีคับจากที่ผ่านมาผมได้เขียนเกี่ยวกับการแกะรอย
วันนี้ก็เลยอยากจะมาอธิบายเทคนิคที่ผมใช้บ่อยๆในการค้นหา IP และการทำ
network mapping ด้วยวิธีการ DNS Zone Transfer ซึ่งเป็นวิธีที่ค่อนข้าง
classic ซักหน่อยนะคับ (อิอิ เก่าแล้วแต่ยังใช้ได้ดีอยู่คับ)

เริ่มกันเลยแล้วกันคับ สมมุติว่าคุณถูกจ้างให้ทำการทดสอบระบบความปลอดภัยของ
องค์กรใดก็ตาม หลังจากที่ได้ใช้ Google ในการค้นหาข้อมูลที่รั่วไหลแล้ว
step ต่อไปก็คือการทำ network mapping หรือการจำลอง network diagram ของ
เป้าหมายโดยที่คุณต้องหาทางให้ได้ข้อมูลนั้นมา อ้าวแล้วจะทำไงดีล่ะคับคราวนี้?
มาดูตัวอย่างกันดีกว่าคับ

องค์กร citXX มี website ชื่อว่า www.citXX.ABC หลังจากที่เราได้ค้นหาข้อมูล
โดยใช้ Google ด้วยคำสั่ง

site:citXX.ABC –site:www.citXX.ABC

คราวนี้เราก็จะได้ sub domain ที่อยู่ภายใต้ domain citXX.ABC มาหลาย domain เช่น

host, kb, blog, rg และอีกมากคับก็ให้จดไว้เป็นข้อมูลเบื้องต้น
หลังจากนั้นถ้าเราจะทำ DNS Zone Transfer เราจะต้องทราบว่า DNS Server
ของเป้าหมายอยู่ที่ไหน โดยปกติแล้วข้อมูลพวกนี้สามารถหาดูได้จาก website ที่ให้บริการ
whois ทั่วๆไปคับ อย่างเช่น www.checkdomain.com, www.apnic.net
ก็จะปรากฏข้อความแบบนี้



อ้าว!!! เฮ้ย….
ไม่มีข้อมูล ทำไงดีล่ะคับคราวนี้ สิ่งที่เราต้องการคือ dns หรือ ip ของ
name server ที่ map ชื่อ www.citXX.ABC อยู่เพื่อทำ zone transfer
อ่อ…. คิอ่อและ หรือว่า dns นี้ไม่ใช่ .com เลยไม่ได้ถูก registered ใน Global whois
งั้นลองค้นหาใน internic ดูดีกว่า ว่าแล้วก็…



ออกมาแล้วครับ สิ่งที่ต้องการนั่นคือ ns1.citXX.ABC หลังจากนั้นก็ให้ลองใช้ nslookup
ในการค้นหา ip address ดูคับ



(ผมขออนุญาตปิดบังข้อมูลนะคับ ทำให้ดูแทบไม่รู้เรื่อง)
ok คับได้ ip address ของ ns1.citXX.ABC มาแล้วพร้อมจะทำ Zone transfer ซะที
แต่เด๋วก่อนไหนลอง nslookup www.citXX.ABC ดูดิว่ามี ip อะไร….
อ้าวดันเป็น ip เดียวกันกับ ns1.citXX.ABC ซะนี่ เป็นไปได้ว่า เครื่องนี้รัน service
ทั้ง web server และ dns server คับ ว่าแล้วก็จดไว้คับ จดไว้..

DNS Zone Transfer
DNS คือ service ที่ให้บริการ map ชื่อ domain กับ ip address เพื่อให้
มนุษย์โลกจำได้ง่ายคับ เช่น ip 58.181.243.6 ชื่อว่า www.sanook.com นะ
พอเวลาที่มนุษย์จะเข้า website หรือใช้บริการอื่นๆก็ไม่จำเป็นใส่ ip address
ก็ให้ใส่ชื่อแทนได้เลยคับ คราวนี้ไอ้เจ้า DNS server นี่แหละที่เป็นตัวเก็บข้อมูลทั้งหมด
ของ Domain และ sub domain ไว้ดังนั้นถ้าเราสามารถเห็นว่ามันเก็บอะไรอยู่บ้าง
เราก็สามารถรู้ได้ว่าชื่อ domain ต่างๆเป็น ip address อะไรรวมทั้งยังเดาได้อีกว่า
ให้บริการอะไรด้วยคับ

ปกติแล้วเราจะใช้คำสั่ง nslookup (name server lookup) เพื่อใช้ในการดูว่า dns นั้น
resolve ออกมาเป็น ip อะไร คราวนี้เราจะมาลองใช้ nslookup เนี่ยแหละทำ
DNS Zone Transfer กันคับโดยพิมพ์คำสั่ง nslookup ใน Terminal ของ windows
จะออกมาเป็นแบบนี้คับ



ให้สังเกตุว่าตอนนี้ Default server ที่ใช้ทำการ dns query นี้คือ ip address router
ของผมเองซึ่งจะไม่มีข้อมูลของเป้าหมายแน่ๆ ดังนั้นเราต้องบอกให้ nslookup ทำการ
query ที่ dns server ของเป้าหมายโดยระบุ ip ที่เราได้ทำการจดไว้ข้างต้น
โดยใช้ทำสั่ง

>server 202.XXX.XXX.XXX



คราวนี้ nslookup ของเราก็จะเข้าใจแล้วว่าจะต้องไปค้นหาข้อมูลต่างๆที่ server ดังกล่าว
หลังจากนั้นเราก็ทำการ set type=any เพื่อบอกว่าเราต้องการทุก record ที่มีนะ
แล้วก็ใช้ทำสั่ง ls –d citXX.ABC. เพื่อเป็นการ list record ทั้งหมดตามรูปนะคับ



ถ้า dns server ไม่ได้ config ไว้อย่างรัดกุมอาจจะทำให้ผลออกมาเป็นแบบนี้คับ



YES!!! ….ออกมาแล้วคับ)
ให้สังเกตุฝั่งซ๊ายมือนะคับตั้งแต่ blog จนถึง www บอกอะไรเราบ้าง
ส่วน column ข้อมูล record type A, NS, MX, CNAME และ SOA นี้จะเป็นการบอกชนิดของ record นะคับว่าเป็นอะไรลองศึกษาการ config DNS server จะทำให้เข้าใจอย่างโจ่งครึ่ม(แจ้ง) ข้อมูลที่ได้มาคือ เครื่องนี้มี name server ชื่อว่า ns1.citXX.ABC ให้บริการ
blog à Web Server
db à Database Server
ftp à FTP Server
mail à Mail Server
ns1 à DNS Server
pop à POP Mail Server
smtp à SMTP Mail Server
www à Web Server
ข้อมูลที่ได้มานี่เป็นทำให้เราสามารถเดาได้ในระดับนึงนะคับว่าเครื่องใดให้บริการอะไรบ้าง
คราวนี้เราลองเอาข้อมูลที่ได้มาวาดรูปดูนะคับว่า network จะเป็นยังไง



นี่คือตัวอย่าง diagram ที่ได้ข้อมูลมาจาก DNS server ที่เราทำ Zone Transfer มาคับ
จริงๆแล้ว services ที่ list ไว้อาจจะตรงหรือไม่ตรงก็ได้เราต้องทำการ check อีกที
โดยการใช้ tools scanner เช่นพวก nmapในการตรวจสอบอีกทีนะคับ

การป้องกันการทำ DNS Zone Transfer นั้นสามารถทำได้โดยการจำกัด host
ที่จะจำเป็นต้องเข้ามาทำ zone transfer เท่านั้นอย่างเช่นพวก DNS secondary server
เท่านั้นที่จะอนุญาตให้เข้ามา query ข้อมูลโดยระบุ ip เครื่องไปเลยคับ

CCNA Final

CCNA 3.1 Semester 1 Final Exam Result Correct 100% (Option 1)

1. Which devices will create multiple collision domains in an Ethernet network? (Choose two.)
Switch router

2. How many collision domains are shown in the diagram?
Seven

3. Refer to the exhibit. The physical documentation shows a portion of the internetwork of the ABC Company. Which segments will be free of collisions?
segments 3, 4, and 5

4. Refer to the exhibit. Which diagram represents the network topology that an administrator would prefer, and why would the administrator prefer it?
Diagram A. It will better provide available bandwidth to the hosts.

5. After an unsuccessful ping to the local router, the technician decides to investigate the router. The technician observes that the lights and fan on the router are not operational. In which layer of the OSI model is the problem most likely occurring?
Physical

6. Refer to the exhibit. How many broadcast domains are shown?
Three

7. Refer to the exhibit. A network associate needs to establish an Ethernet connection between Host A and Host B. However, the distance between the two hosts is further than the cabling standards allow. Which two devices that operate at the physical layer of the OSI can be used to allow Host A and Host B to communicate? (Choose two.)
hub
repeater

8. Refer to the exhibit. What must be configured on Host B to allow it to communicate with the file server? (Choose three.)
a unique host IP address
the subnet mask for the LAN
the default gateway address

9. Refer to the exhibit. Host A pings Host B. What can be concluded about the source and destination addresses contained in the communication sent by Router R5 when it forwards the ping out the Ethernet interface to Host B? (Choose two.)
source MAC address: 5555.AAAA.6666
destination IP address: 192.168.10.134

10. What is the correct number of usable subnetworks and hosts for the IP network address 192.168.35.0 subnetted with a /28 mask?
14 networks / 14 hosts

11. Refer to the exhibit. The network administrator wants to create a subnet for the point-to-point connection between the two routers. Which subnetwork mask would provide enough addresses for the point-to-point link with the least number of wasted addresses?
255.255.255.252

12. Refer to the exhibit. A network technician is trying to determine the correct IP address configuration for Host A. What is a valid configuration for Host A?
IP address: 192.168.100.20; Subnet Mask: 255.255.255.240; Default Gateway: 192.168.100.17

13. Two peer hosts are exchanging data using TFTP. During the current session, a datagram fails to arrive at the destination. Which statement is true regarding the retransmission of the datagram?
Datagram retransmission is controlled by the application.

14. Which protocols are TCP/IP application layer protocols? (Choose two.)
TFTP
DNS

15. When using Category 5 UTP cable, which RJ-45 pin pairs are used to exchange data between hosts on an Ethernet network?
1 and 2; 3 and 6

16. In the exhibit, the connections between the devices are labeled A, B, C, D, and E. For each connection, what is the correct UTP cable to use?
A=rollover, B=straight, C=straight, D=crossover, E=crossover

17. Which cable diagram displays the end to end pinout for a crossover cable used with Cisco devices?
Cable C

18. Which subnet masks could be used when subnetting a Class B IP address? (Choose two.)
255.255.255.240
255.255.192.0

19. Which physical network topology is easy to monitor and troubleshoot, easy to add new devices to as the network expands, but subject to complete failure when a central hub or switch ceases to work?
Star

20. A computer technician is asked to make a network cable. One end of the cable is pinned as a 568A and the other as a 568B. For what purposes can this cable be used? (Choose two.)
to connect a switch to a switch
to connect a hub to a switch

21. Refer to the exhibit. Workstation 1 pings the Fa0/1 interface of Router 1. Which MAC address will workstation 1 obtain during the ARP request for this communication?
00-08-A3-B6-CE-02

22. Refer to the exhibit. A network administrator has configured a network after subnetting the network number 192.168.0.0/28. Workstation 1 is not able to communicate with Workstation 2. What is the cause of this loss in communications?
Workstation 1 is not on the same network that the Router 1 LAN interface is on.

23. Which network device creates the highest amount of latency?

Router

24. An Ethernet host receives a frame, calculates the FCS, and compares the calculated FCS to the FCS received in the frame. The host finds that the two FCS values do not match. What action will be taken by the host?
The host discards the frame.

25. A user initiates three simultaneous FTP connections from the local host to the same FTP server. Which OSI layer is responsible for establishing and managing these different FTP connections?

Session

26. A network administrator has installed a 24 port switch and connected 10 computers with 10/100 NICs. If the NICs are operating at 100 Mbps, how much bandwidth is available for each computer to receive data?

100 Mbps

27. Based on the graphic above, which of the following occurs as each host system comes on line in the topology?
The switch adds MAC address to the bridge table as each host sends a frame.

28. Consider the networks shown in the exhibit. Host A is sending packets to host B. Which layer of the OSI model is being used when the router is making the calculated decision to determine which interface to send the packet out?
Network

29. Why would a company install a switch instead of a hub when building or expanding a corporate network?
A switch provides more bandwidth by sending frames only out the port to which the destination device is attached. A hub sends the frame out all ports except the source port.

30. Refer to the exhibit. The hub and the switch are operating using factory default settings. Which hosts will receive the frame if host A transmits a broadcast frame?
Workstations B, C, D, E, and the router will receive the data.

31. Refer to the exhibit. What kind of Ethernet cable is represented?
straight-through cable

32. The ping command can be used to test connectivity between hosts. Which OSI model layers are verified by this test?
Layers 1, 2 and 3

33. A technician is testing connectivity between the devices using the ping command. Pings between Host B and Host A were successful. The technician could not ping the R3 address 172.16.3.2 from Host A. The technician issued ipconfig from Host A and saw the information displayed in the exhibit. What is the most likely problem?
The default gateway of Host A is incorrect.

34. Why do vendors utilize the OSI model when designing networking products?
It ensures greater compatibility and interoperability with equipment from different vendors.

35. A router determines the path to deliver a packet. What layer of the OSI model does this fact represent?
Network

36. How does a switch learn the addresses of hosts connected to its ports?
The switch reads the source MAC address on incoming frames and records it in CAM.

37. Refer to the exhibit. The connections in the exhibit are labeled A through E. Which of these indicate LAN links? (Choose two.)
link A

link E

38. A large company has a network that is constantly changing. The routing tables in the routers need to be adjusted to reflect the changes in the routing paths. What type of routing would the network administrator implement?
dynamic routing protocols

39. A network administrator has added a new switch to the network. The new switch connects to an existing switch that is already installed. Which UTP cable correctly connects the new switch to the existing switch?
crossover

40. Refer to the exhibit. A newly hired technician has a task of terminating CAT 5 UTP cables. The network administrator visually examined the cables the technician terminated. Some of the cables have connectors as shown in the exhibit. What should the network administrator explain to the technician about the cables?
The cable in Graphic A will produce more crosstalk.

41. Refer to the exhibit. What is the order of the TCP/IP Protocol Data Units as data is moved as indicated through the OSI model?
bits, frames, packets, segments, data

42. Refer to the exhibit. Which type of UTP cable should be used to connect Host A to Switch1?
straight-through

43. Which technologies are considered to be LAN technologies? (Choose two.)
Token Ring

Ethernet

44. Refer to the topology in the graphic. Which characteristic does this type of topology possess? Communication continues in the event of a break in any one connection.

45. Which characteristics are common to both UDP and TCP? (Choose two.)
uses port numbers
classified as a transport layer protocol

46. A router interface has been assigned an IP address of 172.16.192.166 with a mask of 255.255.255.248. To which subnet does the IP address belong?
172.16.192.160

47. Which type of address is 192.168.170.112/28?
subnetwork address

48. What is the decimal representation of the binary number 11111000?
248

49. What are important characteristics to consider when purchasing a network interface card? (Choose two.)
media used on the network system
bus used on the computer

50. Which of the following statements are correct about CSMA/CD? (Choose three.)
It is a media access method used in LANs.
When a device needs to transmit, it checks to see if the media is available.
Only one device can successfully transmit at a time.

===============================================================

CCNA 3.1 Semester 1 Final Exam Result Correct 100% (Option 2)

1 Which devices segment collision domains? (Choose two.)
transceiver
* router
* switch
hub
media

2. Refer to the exhibit. How many collision domains are present in the topology?
3
5
6
* 7
8
9

3. Refer to the exhibit. An instructor in the network class has given the students the network diagram and asks the students to select the appropriate network devices. The goals are to provide a collision-free LAN environment and to provide Internet connectivity. What is the correct design?

Replace Box 1 with a hub and Box 2 with a router.
Replace Box 1 with a router and Box 2 with a bridge.
* Replace Box 1 with a Layer 2 switch and Box 2 with a router.
Replace Box 1 with a router and Box 2 with a Layer 2 switch.
Replace Box 1 with a bridge and Box 2 with a Layer 2 switch.

4. Refer to the exhibit. A network administrator attempts to increase the available bandwidth for workstation A by setting the NIC to full-duplex mode. After the configuration is changed, there are increased collisions and errors occurring. Why is this occurring in the network?

* The NIC is no longer detecting collisions.
The switch will not support full-duplex mode.
The hub will be continually producing a jam signal.
The cabling will not support bidirectional transmissions.

5. Refer to the exhibit. A network administrator is testing a connectivity issue in the network. The administrator discovers that host A cannot communicate with host B, host C, or RouterA. A ping command on host A to 127.0.0.1 succeeds. The NIC link indicator on host A is illuminated. Temporarily, the administrator removes the cable from host A and uses the LAN cable from host B to connect from host A to port 1 on the switch. While using the substitute cable, host A can communicate with host C and RouterA. At which layer of the OSI model was the problem occurring?

session
transport
network
data link
* physical


6. How many broadcast domains are shown in the diagram?

* three
four
five
six
seven
eight

7. A collision has occurred on an Ethernet network. Which three statements explain the CSMA/CD process? (Choose three.)

* After the jam signal, all transmission stops for a random period.
When the collision is detected, the hosts stop transmission immediately.
When the collision is detected, the hosts stop transmission after eight microseconds.
When the backoff period expires, the hosts involved in the collision have priority to transmit.
* When the backoff period expires, each host checks to see whether the networking media is idle and then attempts to transmit.
* When the collision is detected, the hosts continue to transmit using a jam pattern for a short time to ensure that all hosts detect the collision.

8. Which of the following devices extend a collision domain? (Choose two.)

switch
* hub
bridge
router
* repeater

9. What should a network administrator consider when migrating to Gigabit Ethernet architecture from Fast Ethernet? (Choose three.)

* Existing NICs might need to be upgraded.
* Existing switches might need to be upgraded.
Existing NICs must support half-duplex mode.
Existing UTP wiring must be replaced with fiber.
* Existing UTP must be tested for CAT 5e compatibility.
Existing network topology must support shared media.

10. Refer to the exhibit. What must be configured on Host B to allow it to communicate with the Host C? (Choose three.)

the MAC address of RTA router interface connected to Switch 1
* a unique host IP address
the IP address of Switch 1
* the default gateway address
the MAC address of Host C
* the subnet mask for the LAN

11. Which binary number is a representation of the decimal number 248?

11101000
11110100
* 11111000
11111010

12. Which type of address is 223.168.17.167/29?

host address
multicast address
* broadcast address
subnetwork address

13. Workstation A sends data to workstation B. What will have to be altered as the data passes through the router? (Choose two.)

* Layer 1 bit pattern
* Layer 2 frames
Layer 3 packets
Layer 4 segments
Layer 5 -7 data

14. Which combination of network id and subnet mask correctly identifies all IP addresses from 172.16.128.0 through 172.16.159.255?

172.16.128.0 255.255.255.224
172.16.128.0 255.255.0.0
172.16.128.0 255.255.192.0
* 172.16.128.0 255.255.224.0
172.16.128.0 255.255.255.192

15. What is the correct number of usable subnetworks and hosts for the IP network address 192.168.99.0 subnetted with a /29 mask?

6 networks / 32 hosts
14 networks / 14 hosts
* 30 networks / 6 hosts
62 networks / 2 hosts

16. Refer to the exhibit. The internetwork in the exhibit has been assigned the IP address 172.20.0.0. What would be the appropriate subnet mask to maximize the number of networks available for future growth?

255.255.224.0
255.255.240.0
255.255.248.0
* 255.255.252.0
255.255.254.0
255.255.255.0

17. A NIC of a computer has been assigned an IP address of 172.31.192.166 with a mask of 255.255.255.248. To which subnet does the IP address belong?

172.31.0.0
172.31.160.0
172.31.192.0
172.31.248.0
* 172.31.192.160
172.31.192.248


18. What are three characteristics of the TCP protocol? (Choose three.)

exchanges datagrams unreliably
is used to send IP error messages
* forces the retransmission of unacknowledged packets
* creates a virtual session between end-user applications
carries the IP address of the destination host in the TCP header
* is responsible for breaking messages into segments and reassembling them at their destination


19. A network user is using the FTP protocol to transfer data from the local host to an FTP server. The local host is also using the SNMP protocol to report the system status to the network management system. Which statement describes the communication from the host?

FTP and SNMP will use the same port number.
* FTP uses TCP to establish a session before any data is transferred.
The UDP session will reorder the SNMP data as it is received by the network management system.
The TCP protocol for the FTP transfer will use a random destination port number to the FTP server.

20. Which protocols are TCP/IP application layer protocols? (Choose two.)

UDP
* FTP
IP
* SMTP
TCP


21. Which technologies are considered to be WAN technologies? (Choose two.)

Ethernet
* DSL
Token Ring
* Frame Relay
FDDI

22. Refer to the exhibit. What is the order of the TCP/IP Protocol Data Units as data is moved as indicated through the OSI model?

data, segments, frames, packets, bits
data, packets, segments, frames, bits
* data, segments, packets, frames, bits
data, packets, frames, segments, bits

23. Refer to the exhibit. A newly hired technician has a task of terminating CAT 5 UTP cables. The network administrator visually examined the cables the technician terminated. Some of the cables have connectors as shown in the exhibit. What should the network administrator explain to the technician about the cables?

Both cables are acceptable.
* The cable in Graphic A will produce more crosstalk.
The cable in Graphic A should be used in the more critical network segments.
The cable in Graphic A is preferred because it will be easier to crimp the connector.

24. Refer to the exhibit. Which type of UTP cable should be used to connect Switch1 to Switch2?
rollover
console
* crossover
straight-through

25. When using Category 5 UTP cable, which RJ-45 pin pairs are used to exchange data between hosts on an Ethernet network?

1 and 2; 4 and 5
* 1 and 2; 3 and 6
3 and 6; 7 and 8
4 and 5; 7 and 8

26. Refer to the exhibit. Which type of cabling should be used at each of the connection points shown?
A-crossoverB- straight-throughC-straight-throughD-fiberE-straight-through
A-crossoverB-crossoverC-straight-throughD-fiberE-crossover
* A-straight-throughB-crossoverC-straight-throughD-fiberE-straight-through
A-fiberB-crossoverC-straight-throughD-crossoverE-straight-through
A-straight-throughB-crossoverC-crossoverD-fiberE-straight-through
A-crossoverB-crossoverC-straight-throughD-fiberE-straight-through

27. Refer to the exhibit. What type of cable connects the two routers together without any intermediary device?

console
rollover
* crossover
straight-through

28. Which cable diagram displays the end to end pinout for a console cable used with Cisco devices?

Cable A
* Cable B
Cable C
Cable D

29. Which subnet masks would be valid for a subnetted Class B address? (Choose two.)

255.0.0.0
255.254.0.0
255.224.0.0
255.255.0.0
* 255.255.252.0
* 255.255.255.192

30. What type of routing is it when the network administrator manually configures a route?

* static
dynamic
interior
exterior

31. Which statement describes a star topology?

Each host in the network is connected to a backbone cable that is terminated at both ends.
* Each host is connected to a hub or switch, either of which acts as a central point for all network connections.
Each host is directly connected to two other hosts to form a long chain of hosts.
Each host has a connection to all other hosts in the network.

32. Refer to the exhibit. The connections in the exhibit are labeled A through E. Which of these indicate WAN links? (Choose three.)

link A
* link B
* link C
* link D
link E

33. A technician needs to connect a FastEthernet port from a router to a FastEthernet port on a switch. The graphic shows the RJ-45 cable ends for a patch cable. What result can be expected if this cable is used for the link?

* The cable will be able to pass traffic between the devices.
The cable has reversed-pairs, which will degrade the signal quality.
The cable has split-pairs, which will increase crosstalk and create an unreliable link.
The cable has all the wires reversed, which will prevent the link lights from indicating that there is link.

34. Refer to the received frame in the exhibit. In what two ways is the information from the received frame used by a switch? (Choose two.)

192.168.10.5 is used to create an ARP request.
192.168.10.5 is used to build the forwarding table.
1234.5678.1abc is stripped from the frame header.
* 192.168.10.11 is left intact as the frame is forwarded.
The switch compares 192.168.10.11 to the addresses in the routing table to make the forwarding decision.
* To make the forwarding decision, the switch looks in its switch table for address aaaa.bbbb.cccc.

35. Which layer of the OSI model defines the process of adding the source and destination IP address to a data packet?

transport
* network
data link
physical

36. Refer to the exhibit. Workstation 1 pings the Fa0/1 interface of Router 1. Which MAC address will workstation 1 obtain during the ARP request for this communication?

00-06-5B-88-DF-C3
00-B0-D0-7F-F7-46
00-0F-24-85-75-C0
00-0B-E5-64-BD-44
* 00-08-A3-B6-CE-02
00-08-A3-B6-CE-03

37. Refer to the exhibit. What device does Device X represent in the graphic to allow PC1 to ping PC4?

hub
* router
bridge
access point
Layer 2 switch

38. When the receiving workstation detects an error in the data it has received, it does not acknowledge receipt of the data. The source workstation retransmits the unacknowledged data. Which layer of the OSI model supports this process of retransmission?

network
application
session
* transport

39. A company has the following addressing scheme requirements: -currently has 25 subnets -uses a Class B IP address -has a maximum of 300 computers on any network segment -needs to leave the fewest unused addresses in each subnetWhat subnet mask is appropriate to use in this company?

255.255.240.0
255.255.248.0
* 255.255.254.0
255.255.255.0
255.255.255.128
255.255.255.248

40. What can be verified by successfully pinging the reserved loopback address on a host?

Connectivity exists between two hosts on the LAN.
* The TCP/IP stack of the local host is installed correctly.
A connection exists between a host and the default gateway.
The route a packet takes from the local host to a remote host is valid.

41. Refer to the exhibit. A company needs to attach workstation E at a point 150 meters from an existing hub. What device should be placed at location D to allow the new host to connect to the network with the least amount of latency?

router
switch
bridge
* repeater

42. Refer to the exhibit. Which type of Category 5 cable is used to make an Ethernet connection between Host A and Host B?

coax cable
rollover cable
* crossover cable
straight-through cable

43. A simplified CAM table for Switch1 is shown in the exhibit. If host A sends a frame with a destination MAC address of 66C, how does the switch process this frame?

The switch drops the frame.
The switch sends the frame out port 3.
The switch sends the frame out ports 1, 2, and 4.
* The switch sends the frame out ports 2, 3, and 4.
The switch sends the frame out ports 1, 2, 3, and 4.

44. Which of the following increases the potential for a collision to occur?

the use of an active hub instead of an intelligent hub
the use of an intelligent hub instead of an active hub
a reduction in the number of devices attached to the hub
* an increase in the number of devices attached to the hub
2 points for Option 4

45. Refer to the exhibit. Host A has been added to the network. However, host A cannot communicate with the server B or the Internet. All cables have been tested and are functioning to standards. At which layer of the OSI model is this problem occurring?

Layer 1
Layer 2
* Layer 3
Layer 4

46. A workstation is browsing a web server. What will be the partial contents of the segment sent from the workstation to the web server?

* a

47. Refer to the exhibit. What is the purpose of the highlighted address?

* It allows the NIC to communicate with other devices on the same network.
It identifies which part of the IP address is to be considered the network portion.
It provides an address to which all packets that do not have a specific route are sent.
It uniquely identifies the NIC to the free token that is passed on the Ethernet network.

48. Refer to the exhibit. Host A is being manually configured for connectivity to the LAN. Which two addressing scheme combinations are possible configurations that can be applied to the host for connectivity? (Choose two.)

Address - 192.168.1.14 Gateway - 192.168.1.33
Address - 192.168.1.45 Gateway - 192.168.1.33
Address - 192.168.1.32 Gateway - 192.168.1.33
* Address - 192.168.1.82 Gateway - 192.168.1.65
Address - 192.168.1.63 Gateway - 192.168.1.65
* Address - 192.168.1.70 Gateway - 192.168.1.65

49. A user initiates three simultaneous FTP connections from the local host to the same FTP server. Which OSI layer is responsible for establishing and managing these different FTP connections?

application
* session
transport
network
data link

CCNA Module 11

1 What three pieces of information does the transport layer use to manage the communication of separate data streams between hosts? (Choose three.)

*port numbers
checksum values
authentication keys
*sequence numbers
encryption algorithms
*acknowledgment numbers


2 When the receiving workstation detects an error in the data it has received, it does not acknowledge receipt of the data. The source workstation retransmits the unacknowledged data. Which layer of the OSI model supports this process of retransmission?

network
application
session
*transport


3 FTP provides a reliable, connection-oriented service for transferring of files. Which transport layer protocol is used for data transfer when this service is being used?

TFTP
*TCP
DNS
IP
UDP


4 What are the features of the User Datagram Protocol (UDP). (Choose three.)

*no guaranteed delivery of datagrams
connection-oriented
provides reliable full-duplex data transmission
*reliability provided by the application layer
*connectionless
utilizes sliding windowing techniques


5 Which layer of the OSI model can provide a connection-oriented, reliable data transfer between two hosts?

Application
Presentation
Session
*Transport


6 Which Application layer protocol is widely used to support resolving host names to IP addresses?

FTP
SMTP
SNMP
*DNS
HTTP
WWW


7 What does the http portion of the URL http://www.cisco.com/edu/ communicate to a web browser?

The web browser needs to locate the www server.
The address is located on a site whose name is http.
*The web browser is notified as to which protocol to use.
The http portion represents the type of web browser that needs to be used.


8 Which application layer protocol allows network devices to exchange management information?

SMTP
*SNMP
FTP
TFTP
EIGRP




9 Which port numbers are commonly assigned for FTP use? (Choose two.)

19
*20
*21
22



10 An application is using a protocol that exchanges data without using windowing or flow control and must rely on higher layer protocols to transmit data. Which protocol and transfer method are being used?

UDP, connection-oriented
*UDP, connectionless
TCP, connection-oriented
TCP, connectionless
11 TCP is referred to as connection-oriented. What does this mean?

TCP uses only LAN connections.
TCP requires devices to be directly connected.
*TCP negotiates a session for data transfer between hosts.
TCP reassembles the data steams in the order that it is received.




12 Which of the following are primary duties of the OSI transport layer? (Choose two.)

path determination
*end-to-end connectivity
*flow control
security control
data representation
encryption of data


13 What is the purpose of TCP/UDP port numbers?

indicate the beginning of a three-way handshake
reassemble the segments into the correct order
identify the number of data packets that may be sent without acknowledgment
*track different conversations crossing the network at the same time


14 Which protocol is used by e-mail servers to communicate with each other?

FTP
HTTP
TFTP
* SMTP
POP
SNMP


15 Which protocol is used to transfer files from computer to computer but is considered connectionless?

FTP
*TFTP
SNMP
TCP
DHCP

CCNA Module 10

1How does a router decide where the contents of a received frame should be forwarded?

* by matching destination IP addresses with networks in the routing table
by matching the destination IP address with IP addresses listed in the ARP table
by matching the destination MAC address with MAC addresses listed in the CAM table
by forwarding the frame to all interfaces except the interface on which the frame was received




2 Refer to the exhibit. Host A pings host B. When R4 accepts the ping into the Ethernet interface, what two pieces of header information are included? (Choose two.)

source IP address: 192.168.10.129
source IP address: BBBB.3333.5677
source MAC address: 5555.AAAA.6666
destination IP address: 192.168.10.33
*destination IP address: 192.168.10.134
*destination MAC address: 9999.DADC.1234




3 Refer to the exhibit. Host A is connected to the LAN, but it cannot get access to any resources on the Internet. The configuration of the host is shown in the exhibit. What could be the cause of the problem?

The host subnet mask is incorrect.
The default gateway is a network address.
The default gateway is a broadcast address.
*The default gateway is on a different subnet from the host.


4 Refer to the exhibit. A student in the Cisco network class has designed a small office network to enable hosts to access the Internet. What recommendation should the teacher provide to the student in regards to the network design?

Replace the Layer 2 switch with a hub.
*Replace the Layer 2 switch with a router.
Replace the Layer 2 switch with a bridge.
Replace the Layer 2 switch with a transceiver.







5 Refer to the exhibit. A newly hired technician is testing the connectivity of all hosts by issuing a ping command. The technician notices that a default gateway is not configured on all the hosts, but all hosts have connectivity between hosts, a fact which seems to confuse the technician. How would you explain the connectivity to the technician?

The hosts are detecting the default gateway configured on the hub.
*The hosts are all in one LAN, so default gateway information is not needed.
The hosts in the network only require that one host has a gateway configured.
The hosts in the network would only need a gateway if a switch replaces the hub.
The hosts are using broadcast to reach each other since no gateway is configured.


6 A company is using a Class B IP addressing scheme and expects to need as many as 100 networks. What is the correct subnet mask to use with the network configuration?

255.255.0.0
255.255.240.0
*255.255.254.0
255.255.255.0
255.255.255.128
255.255.255.192

7 What do switches and routers use to make forwarding decisions?

Switches and routers both use IP addresses.
Switches and routers use both MAC and IP addresses.
Switches use IP addresses. Routers use MAC addresses.
*Switches use MAC addresses. Routers use IP addresses.
Switches use MAC and IP addresses. Routers use IP addresses.


8 Which device would add security to a network by not forwarding broadcasts?

hub
*router
switch
bridge
repeater


9 Company XYZ uses a network address of 192.168.4.0. It uses the mask of 255.255.255.224 to create subnets. What is the maximum number of usable hosts in each subnet?

6
14
*30
62


10 Host A is connected to the LAN, but it cannot connect to the Internet. The host configuration is shown in the exhibit. What are the two problems with this configuration? (Choose two.)

*The host subnet mask is incorrect.
The host is not configured for subnetting.
The default gateway is a network address.
*The default gateway is on a different network than the host.
The host IP address is on a different network from the Serial interface of the router


11 Refer to the exhibit. A network administrator is planning the addressing scheme for the LAN using 172.25.14.0/26. The hosts are to be assigned addresses 172.25.14.1 – 172.25.14.25. The LAN interface of the router is to be configured using 172.25.14.63 as the IP address. What would describe this addressing scheme?

The LAN is being addressed properly.
The subnet that is being assigned is not a usable subnet address.
*The router LAN interface is being assigned a broadcast address.
The subnet mask does not allow enough host addresses in a single subnet.



12 What is the purpose of a subnet mask in a network?

A subnet mask is not necessary when a default gateway is specified.
A subnet mask is required only when bits are borrowed on a network.
*A subnet mask is used to determine in which subnet an IP address belongs.
A subnet mask is used to separate the 48-bit address into the OUI and the vendor serial number.


13 Refer to the exhibit. The network administrator has assigned the internetwork of LBMISS an address range of 192.168.10.0. This address range has been subnetted using a /29 mask. In order to accommodate a new building, the technician has decided to use the fifth subnet for configuring the new network. By company policies, the router interface is always assigned the first usable host address and the workgroup server is given the last usable host address. Which configuration should be entered into the IP server properties to get connectivity to the network through the router?


IP address: 192.168.10.38 Subnet mask: 255.255.255.240 Default gateway: 192.168.10.39
IP address: 192.168.10.38 Subnet mask: 255.255.255.240 Default gateway: 192.168.10.33
*IP address: 192.168.10.38 Subnet mask: 255.255.255.248 Default gateway: 192.168.10.33
IP address: 192.168.10.39 Subnet mask: 255.255.255.248 Default gateway: 192.168.10.31
IP address: 192.168.10.254 Subnet mask: 255.255.255.0 Default gateway: 192.168.10.1
14 Which statements describe Layer 2 and Layer 3 packet address changes as the packet traverses from router to router? (Choose two.)

Layer 3 header is removed and replaced at every Layer 3 device.
Layer 2 and Layer 3 addresses do not change when the packet traverse.
* Layer 3 source and destination addresses do not change when the packet traverse.
*Layer 2 frame header and trailer are removed and replaced at every Layer 3 device.
Layer 2 source and destination addresses do not change when the packet travels.



15 Which type of routing uses manual entry of information and does not scale well in large internetworks?

interior
exterior
*static
dynamic




16 Given a host with the IP address 172.32.65.13 and a default subnet mask, to which network does the host belong?

172.32.65.0
172.32.65.32
*172.32.0.0
172.32.32.0


17 How does subnetting provide some level of security in a network?

The number of switches must increase.
The collisions prevent the copying of data.
*The broadcasts are contained within a subnet.
The number of host IP addresses is increased.



18 What header address information does a router change in the information it receives from an attached Ethernet interface before information is transmitted out another interface?

only the Layer 2 source address
only the Layer 2 destination address
only the Layer 3 source address
only the Layer 3 destination address
*the Layer 2 source and destination address
the Layer 3 source and destination address



19 At which layer of the OSI model does the device reside that is functioning as the default gateway for hosts on a network?

Layer 1
Layer 2
*Layer 3
Layer 4
Layer 5
Layer 7
20 What is the primary purpose of the routing process?

to propagate broadcast messages
to map IP addresses to MAC addresses
to switch traffic to all available interfaces
to map IP addresses to MAC addresses
*to find paths from one network or subnet to another


21 Refer to the exhibit. A technician is planning an addressing scheme for a branch office as shown in the exhibit. What is the status of the intended network?

The configuration will work as planned.
The subnetwork mask of host A is incorrect.
The default gateway of host A is a network address.
*The addresses on the router LAN interfaces are on the same subnetwork.
The IP address of host A is on a different subnetwork than the subnetwork that the Ethernet router interface is on.


22 Which type of routing allows routers to adapt to network changes?

static routes
* dynamic routing
only default routes
No routing is necessary.


23 Refer to the exhibit. After host 2 is connected to the switch on the LAN, host 2 is unable to communicate with host 1. What is the cause of this problem?

The subnet mask of host 2 is incorrect.
*Host 1 and host 2 are on different networks.
The switch needs an IP address that is not configured.
The router LAN interface and host 1 are on different networks.
The IP address of host 1 is on a different network than is the LAN interface of the router.

24 A company is planning to subnet its network for a maximum of 27 hosts. Which subnet mask would provide the needed hosts and leave the fewest unused addresses in each subnet?

255.255.255.0
255.255.255.192
* 255.255.255.224
255.255.255.240
255.255.255.248




25 An IP network address has been subnetted so that every subnetwork has 14 usable host IP addresses. What is the appropriate subnet mask for the newly created subnetworks?

255.255.255.128
255.255.255.224
*255.255.255.240
255.255.255.248
255.255.255.252

26 What is the primary purpose of a routing protocol?
to propagate broadcast messages
to map IP addresses to MAC addresses
to switch traffic to all available interfaces
*sharing network information between routers

CCNA Module 9

1 Why were private IP addresses developed?

to permit dynamic assignment of IP addresses
to permit the duplication of public IP addresses
to minimize the utilization of reserved IP addresses
to permit public IP addresses to be used in private networks
* to address the issue of not enough available public IP addresses


2 Why is IP considered a best-effort protocol?

IP detects lost packets.
IP validates the content of the packets.
*IP does not provide acknowledgment of the data delivery.
IP reorders the packet as they arrive at the destination host.


3 Which IPv4 class of addresses provides the most networks?

Class A
Class B
* Class C
Class D
Class E


4 Which two statements correctly describe the IP address 127.0.0.1? (Choose two.)

* It belongs to the Class A range of addresses.
It belongs to the Class B range of addresses.
It belongs to the Class C range of addresses.
*It is reserved for loopback testing.
It is reserved for multicast group testing.
It is reserved for unicast testing.



5 What are two facts about how ARP resolves an IP address to a MAC address? (Choose two.)

The originating host dynamically issues an arp –a command to obtain the destination MAC address.
* The originating host broadcasts an ARP request packet and each host in a local network receives this packet.
The originating host dynamically issues an icmp echo request command to obtain the destination MAC address.
*The host with the specified destination IP address sends an ARP reply packet containing its MAC address back to the originating host.
The host with the specified destination IP address sends an icmp echo reply packet to the originating host with its MAC address.
6 Refer to the exhibit. Which devices are recommended to have the IP addresses manually configured?

PC1 and PC2
*all servers
only PC2 Laptop
all hosts and all servers


7 Refer to the exhibit. Which two statements are correct in reference to the output shown? (Choose two.)

The LAN segment is subnetted to allow 254 subnets.
The DNS server for this host is on the same subnet as the host.
*The host automatically obtained the IP addresses 192.168.1.100.
*The host received the IP address from the router on the local LAN segment.
The host is assigned an address of 00-50-8D-F1-EA-8D by the administrator.

8 Refer to the exhibit. The small office LAN shown in the exhibit may eventually be connected to the Internet. According to Cisco best practice, which IP network addresses should be used?

12.0.0.0
172.0.0.0
172.168.0.0
192.32.17.0
*192.168.67.0
225.1.5.0


9 What is the primary responsibility of the transport layer?

allows access to the network media
provides data representation and encoding
selects paths through the network for data to travel
*defines end-to-end connectivity between host applications


10 Refer to the exhibit. Based on the information shown, which two statements are true? (Choose two.)

An ARP request must be used to obtain an address that is placed in the ARP table.
Frames from other hosts in the network to this host will use a destination address of 00-06-25-25-6e-5d.
The only remote locations that can be reached from this host are 192.168.1.97 and 192.168.1.254.
* If a packet is sent to a network device other than 192.168.1.97 and 192.168.1.254, an ARP request must be used.
* If the computer with the IP address of 192.168.1.94 sends a packet to the device with the IP address 192.168.1.97, no ARP request is required.

11 What is the purpose of a DHCP server on a network?

to resolve MAC addresses to IP addresses
to resolve IP addresses to MAC addresses
to resolve host names to IP addresses
*to assign IP addresses dynamically to hosts
to assign a MAC address to a host


12 Which three addresses are considered to be private addresses? (Choose three.)

*10.45.09.23
15.87.234.87
172.32.45.90
*172.17.78.98
192.169.89.56
*192.168.45.23

13 Which statement accurately describes public IP addresses?

Public addresses cannot be used within a private network.
* Public IP addresses must be unique across the entire Internet.
Public addresses can be duplicated only within a local network.
Public IP addresses are only required to be unique within the local network.
Network administrators are free to select any public addresses to use for network devices that access the Internet.


14 Which IPv4 class provides the highest number of host addresses per network?
*Class A
Class B
Class C
Class D
Class E


15 When a host has an empty ARP cache, what is the next step the host will take to find the destination MAC address of a remote host?

sends an ARP request as a unicast to the server
sends an ARP request as a unicast to the destination
*sends an ARP request as a broadcast to all hosts in the local network
sends an ARP request as a unicast to the default gateway







16 Refer to the exhibit. What is the purpose of the Obtain an IP address automatically option shown in the exhibit?

to configure the computer to use ARP
*to configure the computer to use DHCP
to configure the computer to use a routing protocol
to configure the computer with a statically assigned IP address


17 What is the network broadcast address for a Class C address of 192.168.32.0 with the default subnet mask?

192.168.0.0
192.168.0.255
192.168.32.0
192.168.32.254
*192.168.32.255


18 Which subnet mask would be assigned to the network address of 192.168.32.0 to provide 254 useable host addresses per subnetwork?

255.255.0.0
* 255.255.255.0
255.255.254.0
255.255.248.0




19 Which TCP/IP model layer supports both LAN and WAN technologies?

*network access layer
internet layer
transport layer
application layer



20 How many usable hosts are available given a Class C IP address with the default subnet mask?

*254
255
256
510
511
512

CCNA Module 8

1 Two newly hired technicians are discussing the implementation of a new LAN. One technician proposes installing a hub. The other technician advises installing a switch. Which statements are true about the differences between a hub and a switch? (Choose two.)

A hub operates at Layer 2 of the OSI model.
A hub reduces the number of collisions on a LAN.
A hub works at a higher OSI model layer than a switch.
*A switch provides more throughput to hosts on a LAN.
*A switch provides a collision-free environment on a LAN.


2 The number of collisions on a LAN are the same whether a hub or a switch is used.

Refer to the exhibit. Forty-eight workstations are connected to a hub. The users are able to connect to the network, but access is very slow. An entry-level technician replaces the 10 Mbps hub with 100 Mbps hub but the problem still exists. What is the most economical way to correct the problem?

*Replace the hub with a switch.
Replace the hub with a router.
Replace the hub with a 1 Gbps hub.
Replace the hub with a 10 Mbps fiber hub.



3 What is characteristic of the operation of a Layer 2 switch?

selectively drops packets that represent potential security risks
dynamically learns the interfaces to which all devices are attached based on IP address
during switch initialization, queries the devices on all interfaces to learn the MAC addresses of the attached devices
*uses the destination MAC address to determine the specific interface to forward a frame



4 Exhibited is a portion of ABC Company internetwork. Which of the connections can be full duplex?

segments 1 and 2
segment 2
segments 3 and 4
*segments 2, 3, and 4
segments 1, 2, 3, and 4



5 Refer to the exhibit. The switch and the hub have default configurations, and the switch has built its CAM table. Which of the hosts will receive the data when workstation A sends a unicast packet to workstation C?

*workstation C
workstations B and C
workstations B, C, and the E0 interface of the router
workstations B, C, D, E, F, and the E0 interface of the router

6 An administrator would like to connect ten workstations on a 192.168.0.0/24 network. The device selected by the administrator must allow connectivity between hosts without sharing bandwidth. Which device would be appropriate?

hub
router
*switch
repeater

7 Which networking devices use the MAC address to make forwarding decisions? (Choose two.)

NIC
*bridge
hub
*switch
repeater



8 Which devices are primarily used to extend cable segments within a collision domain by regenerating the data signals? (Choose two.)

switch
*repeater
router
bridge
*hub

9 Which devices will create multiple collision domains in an Ethernet network? (Choose two.)

NIC
hub
*switch
*router
repeater





10 Refer to the exhibit. How many broadcast domains exist in classroom 240?

*1
2
5
12
13
15

11 A PC receives a frame. Which situation will cause the NIC on the receiving host to pass the frame contents up the OSI layers to be processed by the PC?

The frame is a runt frame.
*The destination MAC address of the frame is FFFF.FFFF.FFFF.
The transmitting host generated a jam signal during the frame transmission.
The recalculated checksum for the frame does not match the FCS on the frame.

12 A network administrator has a multi-floor LAN to monitor and maintain. Through careful monitoring, the administrator has noticed a large amount of broadcast traffic slowing the network. Which device would you use to best solve this problem?

bridge
hub
*router
transceiver

13 What will a bridge do if it receives a frame with a MAC address that is not within the table?

discard frame
ignore frame
send frame to appropriate port
*send frame to all ports except source port

14 Which networking device reduces the size of both collision domains and broadcast domains?

hub
Layer 2 switch
*router
bridge
repeater

15What is used to prevent Layer 2 switching loops?

bridging
segmentation
Address Resolution Protocol
*Spanning-Tree Protocol


16 What is the function of a Layer 2 switch?
forwards data based on logical addressing
duplicates the electrical signal of each frame to every port
*learns the port assigned to a host by examining the destination MAC address
determines which interface is used to forward a frame based on the destination MAC address

CCNA Module 7

1 Which statements describe Gigabit Ethernet technology? (Choose two.)

operates at 100 Mbps
*typically used for backbone cabling
requires shielded twisted-pair cabling
*can be implemented over copper and fiber
primarily used between workstations option



2 Which of the following are Fast Ethernet technologies? (Choose two.)

100BASE-5
100BASE2
1000BASE-F
*100BASE-FX
*100BASE-TX

3 Which Ethernet standard does the IEEE 802.3 standard recommend for backbone installations?

10BASE-T
100BASE-T
100BASE-FX
*1000BASE-LX



4 What is the maximum distance that 10BASE-T will transmit data before signal attenuation affects the data delivery?

*100 meters
185 meters
300 meters
500 meters


5 At which OSI layer do the differences between standard Ethernet, Fast Ethernet and Gigabit Ethernet occur?

physical layer
*data link layer
network layer
transport layer






6 How does 1000BASE-T use the UTP wire pairs to accomplish transmission?

two pairs are used to transmit and two pairs are used to receive
one pair is used to transmit, one pair is used to receive, one pair is used for clocking, and one pair is used for error correction
*all four pairs are used in parallel by both hosts to transmit and receive simultaneously
two pairs of wires are used as in 10BASE-T and 100BASE-TX


7 What RJ-45 pins are unused when transmitting and receiving data in an Ethernet 100BASE-T Category 5 UTP cable? (Choose two.)

*1 and 2
*3 and 6
4 and 5
7 and 8


8 Which media types can be used in an implementation of a 10BASE-T network? (Choose three.)

*Category 5 UTP
*Category 5e UTP
*Category 3 UTP
coaxial cable
multi-mode fiber
single mode fiber


9 To make sure timing limitations are not violated when implementing a 10 Mbps Ethernet network involving hubs or repeaters, a technician should adhere to which rule?

the 4-5-3 rule
the 6-4-2 rule
the 3-4-5 rule
*the 5-4-3 rule


10 Which of the following Ethernet technologies are considered legacy Ethernet? (Choose three.)

*10BASE2
*10BASE5
*10BASE-T
100BASE-T
100BASE-FX
100BASE-TX

11 Which RJ-45 pins are used to transmit and receive data in an Ethernet 100BASE-TX Category 5 UTP cable? (Choose two.)
*1 and 2
*3 and 6
4 and 5
7 and 8

CCNA Module 6

1 Refer to the exhibit. Host A is communicating with host F. What happens to a frame sent from host A to host F as it travels over the Ethernet segments?

The frame format is modified as it passes through each switch.
*The frame format remains the same across each Ethernet segment.
The frame format is modified as the media speed changed at switch B and switch E.
The frame format is modified as the media material changes between copper and fiber at switch C and switch D.


2 How many hexadecimal digits are in a MAC address?

2
8
*12
16
32


3 What are three functions of a NIC in a PC? (Choose three.)

*A NIC connects the PC to the network media.
* A NIC detects collisions on the Ethernet segment.
A NIC checks the formatting of data before it is transmitted.
* A NIC passes the contents of selected frames to the upper OSI layers.
A NIC acknowledges and retransmits data that was not received properly.
A NIC discards frames when the destination IP address does not match the local host.


4 At what layer of the OSI model does a MAC address reside?

1
*2
3
4
7


5 A router has an Ethernet, Token Ring, serial, and ISDN interface. Which interfaces will have a MAC address?

serial and ISDN interfaces
*Ethernet and Token Ring interfaces
Ethernet and ISDN interfaces
Token Ring and serial interfaces




6 In an Ethernet LAN, how does the NIC know when it can transmit data?

An Ethernet NIC transmits data as soon as the frame is received.
An Ethernet NIC transmits data as soon as the NIC receives a token.
An Ethernet NIC transmits data when it senses a collision.
* An Ethernet NIC transmits data after listening for the absence of a signal on the media.


7 Which characteristics describe carrier sense multiple access collision detect (CSMA/CD)? (Choose three.)

reliable
point-to-point
* nondeterministic
connection-oriented
* collision environment
* first-come, first-served approach




8 Which two devices can provide full-duplex Ethernet connections? (Choose two.)

hub
modem
repeater
*NIC
* Layer 2 switch


9 On a local area network, one workstation can send data on the line while it is receiving data. What type of data transfer does this describe?

hybrid
half duplex
*full duplex
multilink


10 Refer to the exhibit. The small office network shown in the exhibit consists of four computers connected through a hub. Which configuration would cause collisions and errors on the network?

autonegotiation
FastEthernet
peer-to-peer shared resources
*administratively configured full duplex



11 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.


12 Refer to the exhibit. All hosts are in listen mode. Host 1 and Host 4 both transmit data at the same time. How do the hosts respond on the network? (Choose two.)

Hosts 1 and 4 may be operating full duplex so no collision will exist.
The hub will block the port connected to Host 4 to prevent a collision.
*After the end of the jam signal, Hosts 1, 2, 3, and 4 invoke a backoff algorithm.
When the four hosts detect the collision, Hosts 1, 2, 3, and 4 generate a jam signal.
Hosts 1 and 4 are assigned shorter backoff values to provide them priority to access the media.
*If a host has data to transmit after the backoff period of that host, the host checks to determine if the line is idle, before transmitting.



13 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.



14 Which statement describes how CSMA/CD on an Ethernet segment manages the retransmission of frames after a collision occurs?

The first device to detect the collision has the priority for retransmission.
The device with the lowest MAC address determines the retransmission priority.
The devices on the network segment hold an election for priority to retransmit data
*The devices transmitting when the collision occurs DO NOT have priority for retransmission.

15 Refer to the exhibit. A technician wants to increase the available bandwidth for the workstation by allowing the switch and the NIC on the workstation to transmit and receive simultaneously. What will permit this?

CSMA/CD
*full-duplex
FastEthernet
crossover cable




16 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.



17 In which two layers of the OSI model does Ethernet function? (Choose two.)

application
session
transport
network
*data link
* physical



18 Which of the following are specified by IEEE standards as sublayers of the OSI data link layer? (Choose two.)

*Logical Link Control
Logical Layer Control
*Media Access Control
Logical Link Communication
Media Access Communication
Physical Access Communication


19 Where does the MAC address originate?

DHCP server database
configured by the administrator
* burned into ROM on the NIC card
network configuration on the computer
included in the creation of the processor chip

CCNA Module 5

1 Which statement describes a typical use of Gigabit Ethernet?

to provide high-speed desktop connectivity for average users
to provide connectivity to low to medium volume applications
to provide medium volume connectivity to workgroup servers
*to provide high-speed connectivity for backbones and cross connects

2 Which of the following are benefits of a wireless network? (Choose two.)

higher data speeds
better security
*mobility
less expensive NIC cards
*no need to run cables to hosts




3 The ends of a UTP cable are shown in the exhibit. Which cable configuration is shown?

crossover
rollover
reversed-pair
*straight-through
split-pair
console



4 Users with systems that are attached to a hub are complaining about poor response time. What device could replace the hub and provide immediate response time improvement?

router
* switch
bridge
repeater



5 Which function is a unique responsibility of the DCE devices shown in the exhibit?

transmission of data
reception of data
*clocking for the synchronous link
noise cancellation in transmitted data




6 What type of cable would be used to make the connection between the console port of a router and a workstation?

crossover
*rollover
straight-through
patch


7 Which address does a bridge use to make filtering and switching decisions?

source MAC
source IP
*destination MAC
destination IP
network IP address


8 What is the most common type of cabling used in LANs?

STP
*UTP
coax
fiber


9 Refer to the exhibit. What is the appropriate cable to use at each of the numbered network connections?

1-crossover; 2-straight-through; 3-crossover; 4-straight-through
1-straight-through; 2-crossover; 3-straight-through; 4-straight-through
1-straight-through; 2-crossover; 3-crossover; 4-straight-through
*1-rollover; 2-crossover; 3-straight-through; 4-straight-through
1-rollover; 2-straight-through; 3-straight-through; 4-straight-through


10 Refer to the exhibit. A technician measured the lengths of the CAT 5e structured cable runs in the exhibit. How should the technician evaluate the cabling shown in the diagram to the network administrator?

All cabling to work areas are within specifications.
Station A and B may experience intermittent problems because the length exceeds the recommended standard.
*Station B may experience intermittent problems because the length exceeds the recommended standard.
Station C may experience intermittent network connectivity because the length is less than the recommended standard.
Station A and B will have intermittent problems because the length exceeds the recommended standard.
Station C will not have network connectivity because the length is less than the recommended standard.


11 Which of the following are benefits of peer-to-peer networks? (Choose three.)

centralized security
*easy to create
very scalable
*no centralized equipment required
*centralized administrator not required
centralized control of assets


12 In which situations would a crossover cable be used to connect devices in a network? (Choose two.)

switch to PC
*switch to hub
switch to router
switch to server
*switch to switch


13 Which statement is accurate about a WAN link?

*The link transmits data serially.
The link uses a maximum distance of 100 meters.
The link uses the same transmission rate as all other WAN links use.
The link uses the same standardized connector style that is used for all WAN technologies.


14 What device is used to connect hosts to an Ethernet LAN and requires a straight-through UTP cable between the hosts and this device?

NIC
router
*switch
server


15 Which items in the exhibit are DTE devices?

A and B
B and C
C and D
*A and D
A, B, C, and D


16 What is characteristic of the operation of a hub?

selectively drops packets that represent potential security risks
* forwards a frame out all interfaces except the inbound interface
based on IP address, dynamically learns the interfaces to which all devices are attached
upon power on, queries the devices on all interface to learn the MAC addresses of the attached devices
transmits a frame to the specific interface to which the device with the MAC destination address is attached


17 At which layer of the OSI model does the MAC address of a NIC reside?

physical
application
network
transport
*data link
session


18 Which two devices are considered OSI Layer 1 devices? (Choose two.)

*hubs
routers
bridges
switches
*repeaters


19 The ends of a UTP cable are shown in the exhibit. Which cable configuration is shown?

console
*crossover
rollover
reversed-pair
split-pair
straight-through


20 Refer to the exhibit. How many collision domains exist in the network?

1
*2
4
7
8

CCNA Module 4

Module 4
1 What conditions are described when transmission signals from one wire pair affects another wire pair? (Choose two.)

*noise
resistance mismatch
jitter
*crosstalk
attenuation


2 Which of the following are detected by the wire map test? (Choose three.)

near-end crosstalk (NEXT)
*opens
propagation delay
return loss
*reversed-pair faults
*short circuits


3 To ensure reliable LAN communications, what should a technician be looking for when attaching connectors to the ends of UTP cable?

that the white-orange/orange pair is attached first
*that the wire pairs remain twisted as much as possible
that one end of the shield is properly ground but not the other
that 50 ohm termination resistors are on both ends


4 What factors need to be considered to limit the amount of signal attenuation in Ethernet cable runs? (Choose two.)

type of users
number of users
*length of cable
type of electrical equipment
*installation of connectors on the cable



5 Which of the following describes frequency?

length of each wave
height of each wave
*number of cycles each second
amount of time between each wave



6 What is expected when crosstalk is present in networks with higher transmission frequencies? (Choose two.)

jitter
*increase in crosstalk
higher signal attenuation
increases in cancellation effect
*destruction of more of the data signal



7 How are binary ones and zeros represented in fiber optic installations? (Choose two.)

+5 volts/-5 volts
0 volts/5 volts
* light/no light
high to low electrical transition
low to high electrical transition
*increasing/decreasing light intensity
8 What is a cause of crosstalk in UTP cable?

cable pairs that are shorted
cable pairs crossed during termination
cabling runs installed in separate conduit
*cable pairs that are untwisted because of poor termination of the cable


9 A small company is experiencing difficulties on its LAN. After performing some tests, a technician has determined that the copper media supporting the LAN is experiencing abnormal attenuation. What are two possible causes of the problem? (Choose two.)

* defective connectors
*excessively long cable lengths
use of higher grade cabling
low frequency signals used in the media
network cable runs isolated from other cables


10 A company needs to extend the LAN to six separate buildings. To limit the amount of signal attenuation on the LAN media, what type of media would be the best to use between the buildings?

air (wireless)
coaxial cable
*fiber
shielded twisted pair
unshielded twisted pair

CCNA Module 3

1 What is the difference between a wireless NIC and an Ethernet NIC?

The Ethernet NIC operates at 100 Mbps, whereas a wireless NIC operates at 10 Mbps.
The Ethernet NIC uses a PCI expansion slot, and a wireless NIC cannot use an expansion slot.
The wireless NIC uses CSMA/CA, whereas a Ethernet NIC uses token passing as an access method.
*The wireless NIC associates to an access point, and an Ethernet NIC attaches to a hub or switch using a cable.
The Ethernet NIC attaches to a hub or a switch using only fiber cabling, and a wireless NIC attaches to a wireless antenna using air as a network medium.




2 When is a straight-through cable used in a network?

when configuring a router
when connecting a host to a host
*when connecting a switch to a router
when connecting one switch to another switch



3 Refer to the exhibit. The JacksCo is a small start-up company that took over an office space from another small company that closed. The older company left a room of network equipment behind. An inventory list is shown. As the newly hired network technician, you have been asked to determine which components in the storeroom would be best to use to install a small wireless LAN that currently only needs the employees to be able to share data. Note that the wireless LAN also needs to connect to an existing wired LAN. Which components should you choose?


access point and wireless NICs
*wireless NICs, access point, straight-through cables, and a switch
hub, wireless NICs, two wireless bridges, crossover cables, and an access point
wireless NICs, Ethernet NICs, a switch, an external modem, two wireless bridges
Ethernet NICs, wireless NICs, switch, hub, two wireless bridges, straight-through cables, crossover cables, and a router



4 What type of cable is used to make an Ethernet connection between a host and a LAN switch?

console
rollover
crossover
*straight-through


5 A company is converting a cabled LAN to a wireless Ethernet LAN. What must be changed on every host on the network?

No changes are required.
Each host will require a new IP address.
*Each host will require an appropriate NIC or adapter.
Each host will require that the operating system be upgraded.



6 Refer to the exhibit. Which answer correctly identifies the pinout of the UTP cables labeled Cable A, Cable B, and Cable C?

A=straight, B=rollover, C=crossover
A=rollover, B=crossover, C=straight
A=crossover, B=straight, C=straight
*A=crossover, B=straight, C=rollover
A=straight, B=crossover, C=rollover
A=rollover, B=straight, C=crossover


7 What are two advantages of using fiber-optic cabling instead of UTP? (Choose two.)

lower cost
easer to install
*allows longer distances
*less effected by external signals
easier to terminate the cable ends


8 What are two advantages of using UTP cable in a networking environment? (Choose two.)

is stiffer than STP
*is less expensive than fiber
*is easier to install than coaxial
provides longer distances than coaxial provides
is less susceptible to outside noise sources than fiber is


9 Which of the following are used for data communication signals? (Choose three.)

*light patterns
*electrical voltages
controlled air pulses
mixed media impulses
magnetized fluid wave
*Moduleated electromagnetic waves


10 Which Ethernet implementation requires the signal on the media to be boosted at a maximum distance of 100 meters?

10BASE2
10BASE5
*100BASE-T
100BASE-FX
1000BASE-CX


11 Refer to the exhibit. What type of cable connects the two routers together without any intermediary device?

console
rollover
*crossover
straight-through


12 What does UTP cable rely on to reduce signal degradation caused by EMI and RFI?

shielding
magnetism
*cancellation
insulation
properly grounded connections
RJ-45 connectors


13 Select the characteristics specified by 10BaseT. (Choose three.)

*twisted pair cable
T style connectors
* baseband transmission
10 gigabits per second data rate
* 10 megabits per second data rate
decimal encoded data transmission



14 What factors should be considered when selecting the appropriate cable for connecting a PC to a network? (Choose two.)

type of system bus
motherboard model
*distance of cable run
*speed of transmission
computer manufacturer



15 Which cable connectors are used to connect a cable from a router's console port to a PC? (Choose two.)

RJ-11
RJ-12
*RJ-45
DB-8
*DB-9
DB-10

CCNA Module 2

1 Which of the following are factors that determine throughput? (Choose two.)

types of passwords used on servers
type of Layer 3 protocol used
network topology *
width of the network cable
number of users on the network *



2 What is one advantage of defining network communication by the seven layers of the OSI model?

It increases the bandwidth of a network.
It makes networking easier to learn and understand. *
It eliminates many protocol restrictions.
It increases the throughput of a network.
It reduces the need for testing network connectivity.



3 Refer to the exhibit. Which column shows the correct sequence of OSI model layers?

A
B
C
D *



4 Which of the following are data link layer encapsulation details? (Choose two.)

A header and trailer are added. *
Data is converted into packets.
Packets are packaged into frames. *
Frames are divided into segments.
Packets are changed into bits for Internet travel.



5 Which of the following are layers of the TCP/IP model? (Choose three.)

Application *
Physical
Internet *
Network Access *
Presentation


6 What is the term used to describe the transport layer protocol data unit?

bits
packets
segments */
frames
data streams



7 Which three features apply to LAN connections? (Choose three.)

operate using serial interfaces
make network connection using a hub *
limited to operation over small geographic areas *
provide part-time connectivity to remote services
typically operate under local administrative control *
provide lower bandwidth services compared to WANs

8 The central hub has malfunctioned in the network. As a result, the entire network is down. Which type of physical network topology is implemented?

bus
star *
ring
mesh



9 A switch has failed in the network. As a result, only one segment of the network is down. Which type of physical network topology is implemented?

bus
ring
star
extended star *



10 Which of the following are ways that bandwidth is commonly measured? (Choose three.)

GHzps
kbps *
Mbps *
Nbps
MHzps
Gbps *


11 Refer to the following list. Choose the correct order of data encapsulation when a device sends information.
segments
bits
packets
data
frames


1 - 3 - 5 - 4 - 2
2 - 1 - 3 - 5 - 4
2 - 4 - 3 - 5 - 1
4 - 3 - 1 - 2 - 5
4 - 1 - 3 - 5 - 2 *
3 - 5 - 1 - 2 - 4




12 What makes it easier for different networking vendors to design software and hardware that will interoperate?

OSI model *
proprietary designs
IP addressing scheme
standard logical topologies
standard physical topologies




13 Which layer of the OSI model provides connectivity and path selection between two end systems where routing occurs?

physical layer
data link layer
network layer *
transport layer


14 Which term describes the process of adding headers to data as it moves down OSI layers?

division
encoding
separation
segmentation
encapsulation *




15 Which best describes the function of the physical layer?

Defines the electrical and functional specifications for the link between end systems. *
Provides reliable transit of data across a physical link.
Provides connectivity and path selection between two end systems.
Concerned with physical addressing, network topology and media access.


16 Which layer of the OSI model provides network services to processes in electronic mail and file transfer programs?

data link
transport
network
application *

17 Refer to the exhibit. Identify the devices labeled A, B, C, and D in the network physical documentation.

A=bridge, B=switch, C=router, D=hub
A=bridge, B=hub, C=router, D=switch *
A=bridge, B=router, C=hub, D=switch
A=hub, B=bridge, C=router, D=switch



18 Which two features apply to WAN connections? (Choose two.)

operate using serial interfaces *
make network connection using a hub
limited to operation over small geographic areas
typically operate under local administrative control
provide lower bandwidth services compared to LANs *

CCNA Module 1

1What is the binary equivalent for the decimal number 162?

10101010
10100010
10100100
10101101
10110000
10101100

2 Which device connects a computer with a telephone line by providing Moduleation and deModuleation of incoming and outgoing data?

NIC
CSU/DSU
router
modem
telco switch

3 What is the hexadecimal equivalent for the binary number 10001110?

22
67
142
AE
8E

4 What are three conditions that would require a network administrator to install a new NIC? (Choose three.)

whenever a NIC is damaged
when there is a need to provide a secondary or backup NIC
when there is a change from copper media to wireless
whenever operating system security patches are applied
whenever the PC has been moved to a different location


5 What is the binary equivalent for decimal number 149?

10010111
10010101
10011001
10010111
10101011
10101101

6Several computers in the company require new NICs. A technician has located a good price on the Internet for the purchase of these NICs. Before these NICs are purchased and installed, what details must be verified? (Choose three.)

the MAC address on the NIC
the size of the RAM on the NIC
the bandwidth supported by the NIC
the type of media supported by the NIC
the type of network architecture supported by the NIC


7 Convert the binary number 01011011 into its hexadecimal equivalent. Select the correct answer from the list below.

5A
5B
5C
5D
6B
7A




8 Which specialized equipment is used to make a physical connection from a PC to a network?

router
RAM
CD ROM
network interface card


9 Which phrases describe a byte? (Choose two.)

a single binary digit
+5 volts of electricity
the value range 0 to 127
a grouping of eight binary digits
a single addressable data storage location


10 Represented as a decimal number, what is the result of the logical ANDing of binary numbers 00100011 and 11111100?

3
32
35
220
255
11 Convert the decimal number 231 into its binary equivalent. Select the correct answer from the list below.

11110010
11011011
11110110
11100111
11100101
11101110


12 Which of the following are popular web browsers? (Choose two.)

Acrobat
Internet Explorer
Macromedia Flash
Netscape Navigator
Quicktime
World Wide Web




13 Convert the Base 10 number 116 into its eight bit binary equivalent. Choose the correct answer from the following list:

01111010
01110010
01110100
01110110
01110111
01010110




14 In an 8 bit binary number, what is the total number of combinations of the eight bits?

128
254
255
256
512
1024




15 What is the hexadecimal equivalent for the binary number 00100101?

15
20
25
30
37
40

16 What is the binary equivalent for the decimal number 248?

11100000
11110000
11110100 11111000

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ทำไมผู้บริหารจึงควรใส่ใจ และ ดูแลการใช้ email ของพนักงาน ? เป็นคำถามที่น่าสนใจและควรนำมาคิดไตร่ตรองหาคำตอบ เพราะ ในช่วงไม่กี่ปีที่ผ่านมา email ได้กลายเป็นสื่อกลางชนิดใหม่ที่สำคัญในการสื่อสารขององค์กร ไม่ว่าจะเป็นการสื่อสารกับลูกค้า หุ้นส่วนธุรกิจ หรือ แม้แต่กับพนักงานภายในองค์กรด้วยกันเอง ถึงแม้ว่าองค์กรทุกองค์กรต้องการใช้ email ให้เกิดประโยชน์สูงสุดทางธุรกิจ แต่องค์กรยังมีความตระหนักถึงผลกระทบจากการใช้สื่อชนิดใหม่นี้น้อยมาก อาจจะทำให้เกิดผลลบต่อพนักงานและภาพลักษณ์ขององค์กรโดยรวมได้เรื่องการใช้ email ที่ถูกต้องในองค์กรนั้น มีความเข้าใจผิดกันอย่างมาก เพราะว่า ธรรมชาติของ email ซึ่งเป็นสื่อทางอิเล็คโทรนิคส์อย่างไม่เป็นทางการ ทำให้คิดกันไปว่าไม่จำเป็นต้องควบคุมมากนัก ซึ่งไม่เป็นความจริงในทางปฏิบัติ เพราะ ในกฎหมายธุรกรรมอิเล็คโทรนิคส์นั้น email และระบบ Digital Signature นั้นสามารถถือเป็นเอกสารที่ใช้อ้างอิงตามกฎหมายได้ไม่ต่างจากเอกสารประเภทอื่นๆ ดังนั้นองค์กร ทุกองค์กรจึงควรใส่ใจควบคุมการใช้สื่อ email ไม่น้อยไปกว่าการใช้สื่อ ทางธุรกิจประเภทอื่นๆemail address ของพนักงานนั้นไม่ได้แสดงถึงตัวตนของพนักงานเท่านั้น แต่ยังแสดงถึงความเป็นภาพลักษณ์องค์กรโดยรวมอีกด้วย ดังนั้นหากพนักงานใช้ email ของบริษัทในการส่งข้อความหรือ เอกสารที่ไม่เหมาะสมออกสู่สาธารณะ ภาพลักษณ์ด้านลบจะไม่เพียงเกิดขึ้นกับพนักงานผู้นั้น หากแต่จะมีผลกับทบอย่างรุนแรงต่อองค์กรที่พนักงานผู้นั้นทำงานอยู่อีกด้วย ธุรกิจต่างๆมักจะเข้มงวดต่อการส่งจดหมายที่มีการพิมพ์ซอง หรือหัวกระดาษของบริษัท ไม่ให้ส่งในเรื่องส่วนตัว แต่ทำไมถึงได้ปล่อยให้พนักงานส่ง e-mail ออกมาโดยไม่มีการควบคุมที่ดีพอ เป็นเรื่องที่น่าคิดพอสมควรการที่องค์กรไม่มีการควบคุมดูแลการใช้ e-mail นั้นอาจก่อให้เกิดปัญหา การฉ้อโกง การฟ้องร้อง เช่น การเปิดเผย ข้อมูลที่เป็นความลับ การส่งต่อภาพหรือข้อความที่ไม่เหมาะสม ทำให้ธุรกิจเสียภาพลักษณ์ พูดให้ชัดลงไปก็คือ ถ้าองค์กรของคุณยังไม่มีนโยบายสำหรับการใช้ email แล้วละก็ ถึงเวลาที่จะต้องเริ่มมีนโยบายสำหรับการใช้ email ขององค์กรกันแล้วละครับจากมุมมองภายในองค์กร ผู้บริหารมีหน้าที่ในการดูแลพนักงานไม่ให้ใช้ email ในทางที่ผิด หน่วยงาน DTI ของยุโรปได้สำรวจกลุ่มองค์กรธุรกิจของประเทศอังกฤษ พบว่าพนักงานจำนวนถึงเกือบ หนึ่งในสี่ ของพนักงานทั้งหมด ที่ประสบปัญหาจากการล่วงละเมิดทางเพศผ่านทาง e-mail (ทั้งพนักงานชายและหญิง) อย่างไรก็ตาม งานด้านการ จำกัดการใช้ email ในเรื่องส่วนตัวนั้น เปรียบเสมือนการแก้ปัญหาที่เห็นเพียงยอดภูเขาน้ำแข็งเท่านั้น ยังมีงานที่ผู้บริหารต้องทำอีกเป็นจำนวนมาก การไม่ดูแลการใช้ email ในองค์กรนั้นยังเป็นช่องทางให้ข้อมูลที่เป็นความลับในองค์กร ถูกเปิดเผยอีกด้วย พนักงานส่วนใหญ่เมื่อได้รับ email ก็มักจะเปิดอ่านและโหลดไฟล์แนบโดยไม่สนใจว่าเป็น email ที่มาจากใคร ดังนั้น email พวกนี้จีงเป็นที่มาของ spyware,ไวรัส และ โทรจัน ต่างๆ ซึ่งก่อให้เกิดปัญหาระบบเครือข่ายล่ม จนถึง การถูกขโมยข้อมูลผ่านทางโปรแกรมโทรจันซึ่งไม่สามารถตรวจจับได้โดยโปรแกรมกำจัดไวรัส ต้องใช้โปรแกรมกำจัด spyware โดยเฉพาะHacker และ นักเขียนโปรแกรมไวรัส นั้นมีการพัฒนาเทคนิคมากขึ้นทุกๆวัน และ มีการออกแบบข้อความในจดหมายที่น่าสนใจ โดยใช้วิธีปลอมที่อยู่ผู้ส่งให้เป็นคนที่เหยื่อรู้จัก เป็นต้น อุปสรรค์ในการควบคุมการใช้ email ขององค์กรนั้นเกิดจากการที่พนักงานมีการใช้ email จากภายนอกองค์กรมากขึ้น การรับส่ง email ที่เกี่ยวข้องกับงานโดยใช้เครื่องคอมพิวเตอร์ส่วนตัวที่ไม่ได้ติดตั้งโปรแกรมกำจัดไวรัสอย่างถูกต้องนั้นจะทำให้เกิดปัญหาการใช้งานโดยไม่ผ่านกระบวนการด้าน information security ขององค์กรโดยไม่ตั้งใจ จึงไม่ต้องสงสัยเลยว่า พนักงานนั้นเป็นช่องโหว่ด้าน information security ที่ร้ายแรงที่สุดในองค์กร วิธีเดียวที่องค์กรจะสามารถป้องกัน hacker และภัยอื่นๆซึ่งวิ่งผ่านทางระบบดิจิตอลนั้นคือ การอ้างสิทธิในการดูแลขอเปิดอ่าน email ที่น่าสงสัย และการบังคับใช้ นโยบาย email ขององค์กรอย่างจริงจังการมีนโยบายการใช้ email ที่ชัดเจน และ เปิดให้พนักงานทุกคนเข้าถึงได้นั้นยังไม่เพียงพอ หากแต่จะต้องมีการลงนามทำสัญญาอย่างจริงจังด้วย เพื่อทำให้พนักงานทุกคนปฏิบัติตามนโยบายที่กำหนดไว้อย่างเคร่งครัด ยิ่งไปกว่านั้น นโยบายการใช้ email ที่สัมฤทธิผลนั้นไม่เพียงแต่ต้องบังคับใช้ได้ แต่ ยังต้องมีการ ปรับปรุงอย่างต่อเนื่องอีกด้วย เพราะว่า พวก Hacker ที่ใช้เทคนิค Phishing หรือ Pharming และ นักเขียนโปรแกรมไวรัส เองนั้นก็พัฒนาวิธีในการโจมตีหรือล่อลวงอย่างสม่ำเสมอ เช่น การใช้ เทคนิค Social Engineering หลอกเหยื่อเป็นต้น (รายละเอียดเพิ่มเติมดูได้ที่ http://www.antiphishing.org/) ผู้บริหารจึงต้องแก้ไขนโยบายให้ทันสมัยเพื่อให้พนักงานสามารถใช้งาน email ได้อย่างถูกต้อง และ ไม่หลงกลการล่อลวงแบบใหม่ซึ่งมีการอาศัย email เป็นสื่อดังที่กล่าวมาแล้ว
จาก : หนังสือ eLeader Thailandประจำเดือน เดือนมิถุนายน 2548Update Information : 22 มิถุนายน 2548