5.1 Explain the network troubleshooting methodology.

Question 1

Step 1 of the Troubleshooting Theory

Answer 1

IDENTIFY THE PROBLEM

• gather information
• question users
• identify symptoms
• determine if anything has changed
• duplicate the problem, if possible
• approach multiple problems individually

Question 2

Step 2 of the Troubleshooting Theory

Answer 2

ESTABLISH A THEORY OF PROBABLE CAUSE

• question the obvious
• consider multiple approaches
• top to bottom/bottom to top OSI model
• divide and conquer

Question 3

Step 3 of the Troubleshooting Theory

Answer 3

TEST THE THEORY TO DETERMINE THE CAUSE

• if the theory is confirmed, determine the next steps to resolve the problem
• if the theory is not confirmed, reestablish a new theory or escalate

Question 4

Step 4 of the Troubleshooting Theory

Answer 4

ESTABLISH A PLAN OF ACTION TO RESOLVE THE PROBLEM AND IDENTIFY POTENTIAL EFFECTS

Question 5

Step 5 of the Troubleshooting Theory

Answer 5

IMPLEMENT THE SOLUTION OR ESCALATE AS NECESSARY

Question 6

Step 6 of the Troubleshooting Theory

Answer 6

VERIFY FULL SYSTEM FUNCTIONALITY AND, IF APPLICABLE, IMPLEMENT PREVENTIVE MEASURES

Question 7

Step 7 of the Troubleshooting Theory

Answer 7

DOCUMENT FINDINGS, ACTIONS, OUTCOMES, AND LESSONS LEARNED

Question 8

Which of the following protocols does not reside at the application layer of the OSI model?

FTP

HTTP

SMTP

ATM

Answer 8

ATM’s physical layer corresponds to both the physical and data link layer. The physical layer deals with the physical transmission of the bitstream and depends on the physical medium used. Copper cable or fiber optics can be used for ATMs.

HTTP, being an application layer protocol, can run on any underlying protocols, be it TCP/IP, IPX/SPX, UDP, or even on FCP.

FTP is an application layer protocol and can run on any underlying protocols, such as TCP/IP, IPX/SPX, UDP, or even on FCP.

SMTP, being an application layer protocol, can run on any underlying protocols, be it TCP/IP, IPX/SPX, UDP, or even on FCP.

Question 9

An administrator has just finished installing a new switch and connected two servers with IPs of 192.168.105.20 and .30. The servers can communicate with each other but are unable to reach the Internet. What information does the admin see in the switch configuration?

The subnet mask is incorrect

The server is missing default-gateway information

A routing loop has occurred

The admin used a crossover cable to connect the switch to the gateway

Answer 9

The default gateway is the path used to pass information when the device does not know where the destination is. It is a router that connects the host to remote network segments.

A subnet mask is a 32-bit number created by setting host bits to all 0s and setting network bits to all 1s. The subnet mask separates the IP address into the network and host addresses.

A routing loop is formed when an error occurs in the operation of the routing algorithm, and in a group of nodes, the path to a particular destination forms a loop.

A crossover cable is used to connect two Ethernet network devices directly. They are used to send and receive data by enabling complex data transfers.

Question 10

A user took a laptop on vacation and made changes to the configuration in order to use the device at the hotel. The user can reach the Internet, but cannot access any internal network resources. Which of the following is the most likely reason?

Duplicate IP address

Incorrect subnet mask

Incorrect SSID

Incorrect DNS

Answer 10

DNS servers translate domain names into IP addresses, making it possible for DNS clients to reach the origin server. It is the phonebook of the Internet, connecting web browsers with websites. Having an incorrect DNS would cause issues connecting to internal resources as described.

A subnet mask is a 32-bit number created by setting host bits to all 0s and setting network bits to all 1s. The subnet mask separates the IP address into the network and host addresses.

A duplicate IP Address occurs when another device has connected to the network and obtained the same IP address from the DHCP server.

SSID is the unique name that identifies a wireless network.

Question 11

A technician tries the suggested troubleshooting steps to remedy a computer issue. The steps do not fix the problem. Additional suggestions are at a support website that discuss a different cause and potential fix for the problem. What troubleshooting path should the technician follow?

Duplicate the problem, if possible.

Document findings, actions, and outcomes.

Establish a plan of action to resolve the problem and identify potential effects.

If the theory is not confirmed, reestablish a new theory or escalate.

Answer 11

Often problems may have several different possible causes. When a theory is not confirmed, the next in line can be considered. Escalation means referring the problem to a more knowledgeable entity such as a senior technician, manager, or third party.

Establishing a plan of action such as a maintenance window or scheduled down time to fix an issue is best practice. Researching impacts of any fixes should also be considered.

If possible, duplicating the problem is helpful when gathering information about the issue. This includes trying to take the same steps as the user.

Tracking systems, such as a ticketing system, record who is responsible for any given problem and what its status is. This includes a complete description of the problem and its solution, findings, actions, and outcomes.