Lab 9.2.7 Troubleshooting Using Network Utilities

By:Riska Indriana

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. This lab requires setup by the instructor to create various connectivity problems, mainly by enabling and disabling services, disconnecting cables, or using the wrong type of cable (straight-through or crossover). The troubleshooting environment must contain a server with Web, FTP, Telnet, and DNS services installed. The DNS server must be able to resolve the names of the other servers to a common IP address.

The integrated router is both a DHCP client and server and must pass IP address, subnet mask, default gateway, and DNS server information to the client. The internal address should be 192.168.1.x/24, and the external addresses can be determined by the instructor. The external router is configured as a DHCP server to give the integrated router client its IP configuration. The external server should have a static IP configuration. Students have access to the Host-A command line and integrated router GUI, but do not have access to the router or server CLI or GUI.

Problem Scenarios:

1)     Web server software disabled, but physical connectivity to server present.

2)     Web server software enabled and physical connectivity present, but DNS server has incorrect name/address resolution.

3)     FTP server software enabled but physical connection to server not present.

4)     FTP server software enabled and physical connection present, but local host not configured as DHCP client.

5)     Telnet server software enabled, but wrong cable type used to connect the server to the router.

6)     All server software enabled (Web, FTP, Telnet, and DNS) and connections present. Check TCP connections.

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

1. 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.
2. Work from Host-A to issue commands to troubleshoot problems introduced by the instructor.
3. 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.

1. 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? __________________ ipconfig /all

IP address: ________________________________ May vary – 192.168.1.x

Subnet mask: ______________________________ 255.255.255.0

Default gateway IP address: __________________ May vary – 192.168.1.1

DNS server IP address: ______________________ Will vary – IP address of Server set by instructor

DHCP server IP address: _____________________ May vary – 192.168.1.1

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

1. 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: _________________________ Setup > Basic Setup – 192.168.1.1

Subnet mask: ______________________________ 255.255.255.0

Is the DHCP server enabled? __________________ Yes assigned by DHCP server of Router – Set by instructor

Subnet mask: ______________________________ Will vary – Assigned by DHCP server from

Router – Set by instructor

Default gateway IP address: __________________ Will vary – IP address of next hop interface on Router – Set by instructor

DNS server IP address: ______________________ Will vary – IP address of Server – Set by

instructor

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

IP address: ________________________________ Will vary – Static set by instructor

Subnet mask: ______________________________ Will vary – Static set by instructor

Default gateway IP address: __________________ Will vary – Static set by instructor – IP address of next hop interface on Router

Web Server 1 protocol and name: ________________________ (May vary – Live CD server name is http://server-1.discovery.ccna

Web Server 2 protocol and name: ________________________ (May vary – Live CD server name is http://server-1.discovery.ccna

FTP Server 1 protocol and name: ________________________ (May vary – Live CD server name is http://server-1.discovery.ccna

FTP Server 2 protocol and name: ________________________ (May vary – Live CD server name is          http://server-1.discovery.ccna

Step 3: Scenario 1—Diagnose Web server access

1. After your instructor sets up the problem for this scenario, use various utilities to diagnose the problem.
2. Open your browser and enter the name of the Web Server 1 from Step 2. What happened?…. Host-A is unable to reach the server website
3. Which commands did you use to diagnose the problem? ….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? Problem: Web server software was disabled. Network connectivity tested good. DNS is working. Must be problem with the HTTP server
5. What did you do to correct the problem, if anything? Nothing student can do but report suspected problem to instructor to start HTTP server
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 4: Scenario 2—Diagnose Web server access

1. After your instructor sets up the problem for this scenario, use various utilities to diagnose the problem.
2. Open your browser and enter the name of the Web Server 2 from Step 2. What happened? Host-A is unable to reach the server website
3. Which commands did you use to diagnose the problem? 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
4. Report the problem or suspected problem to the instructor. What was the problem? 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
5. What did you do to correct the problem, if anything? 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
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 5: Scenario 3—Diagnose FTP server access

1. After your instructor sets up the problem for scenario, use various utilities to diagnose the problem.
2. Use your FTP client (CLI or GUI) to connect to FTP Server 1 from Step 2. What happened? …… Host-A is unable to reach the FTP site
3. Which commands did you use to diagnose the problem? 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.
4. Report the problem or suspected problem to the instructor. What was the problem? 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
5. What did you do to correct the problem, if anything?  ……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

1. After your instructor sets up the problem for this scenario, use various utilities to diagnose the problem.
2. Use your FTP client (CLI or GUI) to connect to FTP Server 2 from Step 2. What happened? ….. Host-A is unable to reach the server FTP site
3. Which commands did you use to diagnose the problem? …. 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
4. Report the problem or suspected problem to the instructor. What was the problem?…. 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 noncompatibl static address. Host-A should be a DHCP client
5. What did you do to correct the problem, if anything? Configure Host-A as DHCP client, 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 7: Scenario 5—Diagnose Telnet server access problem

1. After your instructor sets up the problem for this scenario, use various utilities to diagnose the problem.
2. Use a Telnet client (CLI or GUI) to connect to the name of Server 1 identified in Step 2. What happened?…………………….. Host-A is unable to reach the Telnet server
3. Which commands did you use to diagnose the problem? ……………….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
4. Report the problem or suspected problem to the instructor. What was the problem? 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? ……….. Replace the straight-through cable from server to router with a crossover cable and retest
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 8: Scenario 6—Analyze TCP connections to Host-A

1. 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.
2. 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? netstat
3. Which named connections did you see? HTTP, FTP, Telnet, and possibly others
4. 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?  netstat -n
5. Which IP addresses and port numbers did you see? Should see the foreign IP address of the server and ports 80 (HTTP), 21 (FTP), 23 (Telnet), and possibly others.
6. 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? ……netstat -b
7. Which program executable (filename with an .exe extension) is listed for each of the connections? ……….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

1. When troubleshooting the problem scenarios during this lab, which troubleshooting technique did you use primarily (top-down, bottom-up, or divide and conquer)?……..Answers will vary – Mostly top-down
2. Which utility or command do you feel was the most useful for network troubleshooting? …..Answers will vary – probably ping