CCNA Discovery 1 chapter 9

Lab 9.2.7 Troubleshooting Using Network Utilities

Objectives

·       Use network utilities and the integrated router GUI to determine device configurations.

·       Select the appropriate network utilities to help troubleshoot connectivity problems.

·       Diagnose accessibility problems with Web, FTP, Telnet, and DNS servers.

·       Identify and correct physical problems related to cable types and connections.

Background / Preparation

In this lab, you use the browser and various troubleshooting utilities, such as ipconfig, ping, tracert, netstat, and nslookup to diagnose and correct connectivity problems. These command line interface (CLI) utilities are available on most current operating systems, although the exact command and syntax may vary. Windows XP commands and syntax are used in this lab.

Your instructor will set up the network topology similar to the one shown here and will preconfigure the client computer, integrated router, server, and external router for each scenario in the lab. Various software and hardware connectivity problems will be introduced, and you will diagnose the cause from the client computer.

There are six scenarios. Work in teams of three, with each person taking the lead in two of the scenarios, and the other team members assisting.

The following resources are required:

·       Computer running Windows XP Professional with Web, FTP, and Telnet clients (CLI or GUI).

·       Server running a combination of DNS, HTTP, FTP, and Telnet services (preconfigured). This server will simulate Internet connections and can be a server with these services actually installed and running or a server running the Discovery Live CD.

·       Integrated router configured as a DHCP server and client (default configuration).

·       Router with two Ethernet interfaces configured as a DHCP server to integrated router (preconfigured).

·       Ethernet Cat-5 (minimum) straight and crossover cabling to connect hosts and network devices.

Step 1: Build the network and configure the hosts

a.       Have your instructor set up a network topology similar to the one shown with the Host-A client computer, integrated router, server, and router preconfigured.

b.       Work from Host-A to issue commands to troubleshoot problems introduced by the instructor.

c.        All commands are issued from a command prompt window. Open a command prompt window by clicking Start > All Programs > Accessories > Command Prompt. Keep the window open for the duration of the lab.

Step 2: Record the baseline IP address information for computers and integrated router

NOTE: Perform this step before the instructor introduces problems.

a.          Host-A configuration—Issue the command that displays the IP address information for Host-A, including the DNS server, and record the information below. Which command did you use?

IP address: 192.168.1.23

Subnet mask: 255.255.255.0

Default gateway IP address: 192.168.1.1

DNS server IP address:

DHCP server IP address: 192.168.1.1

How did Host-A obtain its IP address? DHCP from integrated router

b.       Integrated router configuration—From Host-A, open a browser and go to the integrated router GUI by entering 192.168.1.1 as the URL address. Log in to the integrated router using the default user ID and password (check with your instructor if necessary). Check the internal and external IP address information and record it below.

Internal IP address: 192.168.1.1

Subnet mask: 255.255.255.0

Is the DHCP server enabled? Yes

External (Internet) IP address:

Subnet mask:

Default gateway IP address:

DNS server IP address:

Server configuration—Obtain the Server IP configuration from your instructor and record the information below.

IP address:

Subnet mask:

Default gateway IP address:

Web Server 1 protocol and name:

Web Server 2 protocol and name:

FTP Server 1 protocol and name:

FTP Server 2 protocol and name:

Step 3: Scenario 1—Diagnose Web server access

a.       After your instructor sets up the problem for this scenario, use various utilities to diagnose the problem.

b.       Open your browser and enter the name of the Web Server 1 from Step 2. What happened? Jawab: Host-A is unable to reach the server website

c.        Which commands did you use to diagnose the problem? Jawab: Browse by name and IP fails; 2. Ping server by name succeeds

4. Report the problem or suspected problem to the instructor. What was the problem? Jawab; Problem: Web server software was disabled. Network connectivity tested good. DNS is working. Must be problem with the HTTP server

e.        What did you do to correct the problem, if anything? Jawab: Nothing student can do but report suspected problem to instructor to start HTTP server

f.        You may need to contact the instructor to correct the problem. When the problem is corrected, retest and verify access to the server.

Step 4: Scenario 2—Diagnose Web server access

a.       After your instructor sets up the problem for this scenario, use various utilities to diagnose the problem.

b.       Open your browser and enter the name of the Web Server 2 from Step 2. What happened? Jawab : Host-A is unable to reach the server website

3. Which commands did you use to diagnose the problem? Jawab : 1. Browse by name fails. 2. Browse by IP succeeds. 3. Ping by name fails. 4. Ping by IP succeeds. nslookup for http://server-2.discovery.ccna reveals that the server name is associated with the wrong IP address

d.       Report the problem or suspected problem to the instructor. What was the problem? Jawab :

Web server software enabled and physical connectivity present, but DNS server has incorrect

name/address resolution

Browser can get to web server by IP but not by name. Network connectivity tested good. Suspected DNS server could be down, but nslookup discovered bad entry in DNS table

e.        What did you do to correct the problem, if anything? Jawab:

Nothing student can do but report suspected problem to instructor, or student can browse to http://server-1.discovery.ccna, which resolves to the correct IP address. If DNS is running stale

information, solution could be to wait for information to expire and then flush tables (not possible without admin access) or redirect client to another name server

f.        You may need to contact the instructor to correct the problem. When the problem is corrected, retest and verify access to the server.

Step 5: Scenario 3—Diagnose FTP server access

a.       After your instructor sets up the problem for scenario, use various utilities to diagnose the problem.

b.       Use your FTP client (CLI or GUI) to connect to FTP Server 1 from Step 2. What happened? Jawab : Host-A is unable to reach the FTP site

c.        Which commands did you use to diagnose the problem? Jawab:

1. FTP client to server by name fails. 2. FTP client by IP fails. 3. Ping to server by name or IP fails. 4. Ipconfig on Host-A shows correct IP info. Tracert to server fails at router connected to server

d.       Report the problem or suspected problem to the instructor. What was the problem? Jawab:

FTP server software enabled, but physical connection to server not present FTP and ping network connectivity testing failed. Host-A IP config is OK. Traceroute indicated problem at router connected to server. Visual inspection reveals cable to server NIC is disconnected

e.        What did you do to correct the problem, if anything? Jawab: Connect cable to server NIC and retest to verify that this is the only problem

6. You may need to contact the instructor to correct the problem. When the problem is corrected, retest and verify access to the server.

Step 6: Scenario 4—Diagnose FTP server access

a.       After your instructor sets up the problem for this scenario, use various utilities to diagnose the problem.

b.       Use your FTP client (CLI or GUI) to connect to FTP Server 2 from Step 2. What happened? Jawab: Host-A is unable to reach the server FTP site

c.        Which commands did you use to diagnose the problem? Jawab:

1. FTP client to server by name fails. 2. FTP client by IP fails. 3. Ping to server by name or IP fails. 4. Ping to default gateway (integrated router internal address) fails. 5. Ipconfig on Host-A shows incorrect static IP info. 6. Tracert fails at integrated router

d.       Report the problem or suspected problem to the instructor. What was the problem? Jawab:

Problem: FTP server software enabled and physical connection present, but local host has wrong

static IP address and not configured as DHCP client

FTP and ping to server testing failed. The ipconfig command indicated that Host-A had noncompatible static address. Host-A should be a DHCP client

e.        What did you do to correct the problem, if anything? Jawab: Configure Host-A as DHCP client, and retest to verify that this is the only problem

f.        You may need to contact the instructor to correct the problem. When the problem is corrected, retest and verify access to the server.

Step 7: Scenario 5—Diagnose Telnet server access problem

a.       After your instructor sets up the problem for this scenario, use various utilities to diagnose the problem.

b.       Use a Telnet client (CLI or GUI) to connect to the name of Server 1 identified in Step 2. What happened? Which commands did you use to diagnose the problem? Jawab: Host-A is unable to reach the Telnet server

c.        Report the problem or suspected problem to the instructor. What was the problem? Jawab:

1. Telnet client to server by name fails. 2. Telnet client to server by IP fails. 3. Ping to server by name or IP fails. 4. Ping to default gateway (integrated router internal address) succeeds. 5. Ipconfig on Host-A shows correct IP info. Tracert to server fails at router connected to server

d.       What did you do to correct the problem, if anything? Jawab:

Problem: Telnet server software enabled, but the wrong cable type (straight-through) used to connect the server. Server NIC and router interface are both hosts and are considered to be like devices. Should be a crossover instead of a straight-through cable, because there is no switch or hub in between

Telnet and ping to server testing failed. Host-A IP config is OK and Host-A can ping its default

gateway. Traceroute indicated problem at router connected to server. Visual inspection reveals cable to server NIC is wrong type

5. What did you do to correct the problem, if anything? Jawab:

Replace the straight-through cable from server to router with a crossover cable and retest

f.        You may need to contact the instructor to correct the problem. When the problem is corrected, retest and verify access to the server.

Step 8: Scenario 6—Analyze TCP connections to Host-A

a.       Ask your instructor to verify that all problems introduced with the lab setup have been corrected. Using the appropriate clients, connect to the Web, FTP, and Telnet servers simultaneously from Host-A.

b.       From the command line, issue a command to display the current active TCP connections to Host-A with names of the servers and protocols. Which command did you use?jawab:  netstat

c.        Which named connections did you see? Jawab : HTTP, FTP, Telnet, and possibly others

d.       From the command line, issue a command to display the current active TCP connections to Host-A with IP addresses and protocol port numbers. Which command did you use? Jawab : netstat -n

5. Which IP addresses and port numbers did you see? Jawab : Should see the foreign IP address of the server and ports 80 (HTTP), 21 (FTP), 23 (Telnet), and possibly others.

f.        From the command line, issue a command to display the current active TCP connections to Host-A, along with the program that created the connection. Which command did you use? Jawab : netstat -b

g.        Which program executable (filename with an .exe extension) is listed for each of the connections?jawab :

Executables for each client (GUI or CLI) used to initiate the connection: iexplore.exe, ws-ftp.exe, ftp.exe, telnet.exe, and so on.

Step 9: Reflection

a.        When troubleshooting the problem scenarios during this lab, which troubleshooting technique did you use primarily (top-down, bottom-up, or divide and conquer)? Jawab : divide and conquer

b.       Which utility or command do you feel was the most useful for network troubleshooting?

Lab 9.3.3 Troubleshooting Physical Connectivity

Objectives

·       Examine device LEDs to determine proper Ethernet connectivity.

·       Select the correct Ethernet cable for use between various types of devices.

·       Visually inspect cables for potential problems.

·       Use a cable tester to help identify cabling problems.

Background / Preparation

Physical cabling is one of the most common sources of network problems. This lab focuses on connectivity issues related to network cabling. You will visually inspect cabling and LED link lights to evaluate physical connections and to determine if the correct type of cable is being used based on the devices they interconnect. You will also use a cable tester to identify problems with cables.

The instructor will set up the network topology similar to the one shown and will preconfigure the hosts and network devices. The instructor will introduce various connectivity problems, and you will diagnose the cause of these problems by inspecting link lights and testing cables between devices. Various cable types, both good and bad, will be used to interconnect devices for each scenario in the lab.

Work in teams of two, with each person taking the lead in half of the problem scenarios.

The following resources are required:

·       Computer running Windows XP Professional (preconfigured)

·       Server (preconfigured)

·       Integrated router configured as a DHCP server and client (default configuration)

·       Router with two Ethernet interfaces configured as the DHCP server to integrated router (preconfigured)

·       Mix of Ethernet Cat-5 (minimum) straight-through and crossover cabling, both good and bad, to connect hosts and network devices

·       Basic Cat-5 Ethernet cable tester (RJ-45 pin-to-pin continuity checker)

·       Advanced cable tester (optional), such as Fluke 620 (or similar)

Step 1: Build the network and configure the hosts

a.       Ask your instructor to set up a network topology similar to the one shown with a preconfigured Host-A client computer, integrated router, server, and router. Initially, correct and properly functioning cabling is used so that end-to-end connectivity can be verified. The instructor then introduces cabling problems in each scenario.

b.       Problems can consist of using the wrong type of` cable between two devices (straight-through or crossover) or using a defective cable (miswired or improperly terminated). Observe device interface link lights, visually inspect cables, and use a cable tester to determine the problems.

c.        Complete steps 2 and 3 of this lab before the instructor introduces problems.

Step 2: Record the correct cable types used between devices

a.       Refer to the topology diagram and record the cable type that should be used (straight-through or crossover) based on the devices being connected. Have your instructor verify this information before proceeding.

b.       Which type of cable should be used from Host-A to the integrated router? Jawab : Straight-through cable

c.        Which type of cable should be used from the integrated router (router portion) to Hub/Switch? Jawab : Straight-through cable

d.       Which type of cable should be used from Hub/Switch to Router? Jawab: Straight-through cable

e.       Which type of cable should be used from Router to Server? Jawab : Crossover cable

Step 3: Record the IP address information for the computers

a.       Use the ipconfig command, or get the IP address of Host-A from your instructor, and record it here.

Host-A IP address: DHCP 192.168.1.5

2. Get the server IP address from your instructor and record it here.

Server IP address: 192.168.1

3. Before starting on problem scenarios, verify end-to-end connectivity by pinging from Host-A to Server. If you do not get a reply from the server, check with your instructor. There may be a problem with the initial hardware or software setup.

Step 4: Scenario 1

a.       After your instructor sets up the problem, use visual inspection and a cable tester to isolate the problem.

b.       Ping from Host-A to Server. What happened? Jawab : Host-A is unable to reach destination host (Server).

c.        Check the LED link lights on the various device interfaces. Write down any that are not lit. jawab:

Host-A NIC LED and LED on front of integrated router switch that corresponds to the port where host- A is connected.

d.       Disconnect and inspect the cable connecting the network interfaces that were not lit. Describe the problem and how you were able to identify it. Jawab

Problem: Incorrect cable type between Host-A and integrated router (Crossover instead of a straightthrough)

Visual inspection could reveal an incorrect cable type based on those identified in Step 2. A basic

cable tester would show that wire continuity was good but that this is a crossover cable. A straightthrough cable should be used for connecting a host to a hub/switch (or switch port of the integrated router)

e.        What did you do to correct the problem? Jawab: Replaced the crossover cable with a straight-through cable

f.       When the problem is corrected, retest and verify end-to-end connectivity by pinging from Host-A to Server. Was the ping successful? Jawab : ya

Step 5: Scenario 2

a.       After your instructor sets up the problem, use visual inspection and a cable tester to isolate the problem.

b.       Ping from Host-A to Server. What happened? Jawab : Host-A is unable to reach destination host (Server)

c.        Check the LED link lights on the various device interfaces. Write down any that are not lit. jawab: Router Ethernet interface link LED, and LED on Server NIC

d.       Disconnect and inspect the cable connecting the network interfaces that were not lit. Describe the problem and how you were able to identify it.  Jawab:

Problem: Miswired straight-through cable between Hub/Switch and Router (incorrect pinouts –

send/receive on wrong pins).

Visual inspection could reveal incorrect cable pinouts. A basic cable tester would show that cable

continuity was good but that send/receive wires (those that go to pins 1, 2, 3, or 6) are going to the wrong pins. A straight-through cable is used for connecting a host router interface to a hub/switc

e.        What did you do to correct the problem? Jawab: Replaced the miswired cable with a tested straight-through cable

f.       When the problem is corrected, retest and verify end-to-end connectivity by pinging from Host-A to Server. Was the ping successful? Jawab : ya

Step 6: Scenario 3

a.       After your instructor sets up the problem, use visual inspection and a cable tester to isolate the problem.

b.       Ping from Host-A to Server. What happened? Jawab: Host-A is unable to reach destination host (Server).

c.        Check the LED link lights on the various device interfaces. Write down any that are not lit. jawab: Server NIC LED, and LED on Router Ethernet interface.

d.       Disconnect and inspect the cable connecting the network interfaces that were not lit. Describe the problem and how you were able to identify it. Jawab:

Problem: Incorrect cable type between Router and Server (straight-through instead of crossover).

Visual inspection could reveal an incorrect cable type based on those identified in Step 2. A basic

cable tester would show that wire continuity was good but that this is a straight-through cable. A

crossover cable is used for connecting two hosts (or like devices). The router Ethernet interface and the Server NIC are considered like devices.

e.        What did you do to correct the problem? Jawab : Replaced the straight-through cable with a crossover cable

f.        When the problem is corrected, retest and verify end-to-end connectivity by pinging from Host-A to Server. Was the ping successful? Jawab: ya

Step 7: Scenario 4

a.       After your instructor sets up the problem, use visual inspection and a cable tester to isolate the problem.

b.        Ping from Host-A to Server. What happened? Jawab: Host-A is unable to reach destination host (Server)

c.         Check the LED link lights on the various device interfaces. Write down any that are not lit. jawab: Integrated router Internet interface link LED, and LED on hub/switch port to which it is connected

d.       Disconnect and inspect the cable connecting the network interfaces that were not lit. Describe the problem and how you were able to identify it. Jawab:

Problem: Improperly terminated cable between integrated router and Hub/Switch (open on

send/receive wires to pins 1, 2, 3, or 6 at RJ-45 connector).

Visual inspection could reveal cable open connection at RJ-45 connector. A basic cable tester would show that that the cable continuity failed on the wires where the open occurred. A straight-through cable is used for connecting the router Ethernet (Internet) interface from the integrated router to the hub/switch.

e.        What did you do to correct the problem? Jawab: Replaced the improperly terminated cable with a tested straight-through cable

f.        When the problem is corrected, retest and verify end-to-end connectivity by pinging from Host-A to Server. Was the ping successful? Jawab : ya

Step 8: Reflection

1. What are some general rules to help you determine which type of Ethernet cable (straight-through or crossover) to use to connect different types of network hosts and devices? Jawab: Direct connections between similar devices (computer-to-computer, hub-to-hub, hub-to-switch, router-to-router, and so on) typically require a crossover cable. Remember that a router interface is considered a host. Direct connections between dissimilar devices (computer-tohub, computer-to-switch, router-to-hub or switch, and so on) typically require a straight-through cable.

b.       Which types of problems can a cable tester detect that might not be determined by visual inspection? Jawab: some shorts, opens