| Lab 4.4.4 Traceroute command Estimated time: 30 min. Objectives: Use the traceroute Cisco IOS command from source router to destination router. Use the tracert Windows OS command from source workstation to destination router. Use the show ip route command to display the router's routing table. Verify that the network-layer between source, destination and each router along the way is working. properly. Retrieve information to evaluate the end-to-end path reliability. Determine delays at each point over the path and whether the host can be reached. Background: In this lab you will use the IOS traceroute command. The traceroute command uses ICMP packets and the error message generated by routers when the packet exceeds its Time To Live (TTL). When you initiate the trace command to a target host the router sends an ICMP echo-request packet with the TTL set to one (1). The first router in the path to the target host receives the ICMP echo-request packet and sets the TTL to zero (0). The first router then sends an ICMP Time-exceeded message back to the source. The source router then sends an ICMP echo-request packet with the TTL set to two (2). The first router receives the ICMP echo-request and sets the TTL to one (1) and sends it to the next router in the path to the target host. The second router receives the ICMP echo-request and sets the TTL to zero (0) then sends an ICMP Time-exceeded message back to the source. The source then sends an ICMP echo-request with a TTL set to 3. This cycle continues until an ICMP echo-reply is received from the target host or until a ICMP destination-unreachable message is received. This allows you to determine the last router to be reached in the path to the target host. This is a troubleshooting technique called fault isolation. Tools / Preparation: Prior to starting the lab you will need to connect a PC workstation with HyperTerminal to a router using the routers console Interface with a roll-over cable. This lab should be done at the router console station. You may want to review Chapter 13 in the Cisco Networking Academy First-Year Companion Guide and review semester 2 online chapter 4 prior to starting this lab. Work individually or in teams. Be familiar with the following commands: traceroute ip xxx.xxx.xxx.xxx - (Where xxx.xxx.xxx.xxx is the IP address of the host you want to trace). The ip after the command is the default and may be omitted. traceroute hostname (Where host name is a name that can be resolved to an IP address). traceroute is a Cisco IOS command. tracert xxx.xxx.xxx.xxx - (Where xxx.xxx.xxx.xxx is the IP address of the host you want to trace). tracert hostname - (Where host name is a name that can be resolved to an IP address). tracert is a Windows 95/98 or NT command. show ip route - This will show you the IP routing table - the directions that the router uses to determine how it will direct traffic across the network. Resources Required: PC with monitor, keyboard, mouse, and power cords etc. Windows operating system (Win 95, 98, NT or 2000) installed on PC HyperTerminal program Access to multiple routers Websites Sites Resources: Routing basics General information on routers 2500 series routers 1600 series routers Terms and acronyms IP routing protocol IOS command summary Beginning IP for new users Notes: Step 1 - Log on to router. Explanation: Connect to the router and login. Enter the password cisco if prompted. 1. a. What prompt did the router display? b. What does it mean? Step 2 - Enter trace (abbreviated form of traceroute). Task: Enter trace at the router prompt. 2. What did the router respond with? Step 3 - Enter trace ? Task: Enter trace ? at the router prompt. 3. What did the router respond with? Step 4 - Get help with trace ip command. Task: Enter trace ip ? at the router prompt. 4. What did the router respond with? Step 5 - Trace route from end router to end router. Task: Enter trace ip xxx.xxx.xxx.xxx where xxx.xxx.xxx.xxx is the IP address of the target destination. Note: You will want to do this lab using one of the end routers and trace IP to the other end router. (note: ip is the default) Explanation: Trace command is the ideal tool for finding where data is being sent in your network. 5. a. List the host name and IP address of the routers that the ICMP packet was routed through.
Host Name | IP Address
Step 6 - Trace the route to all other routers on your network. Task: Repeat Step 5 with all other routers on your network. Step 7 - Use tracert from a MS-DOS command prompt. Task: From the console workstation click on Start/Programs/MS DOS Command Prompt. An MS-DOS Command Prompt window will open up. Enter tracert and the same IP address that you used in step 5. Explanation: By using the MS-DOS window you will be using the TCP/IP stack of the workstation to begin the trace to the destination. The first hop will be your default gateway or the near side router interface on the LAN that the workstation is connected to. 6. a. List the host name and IP address of the router that the ICMP packet was routed through.
Host Name | IP Address
b. Why is there one more entry in the output of the tracert command when you trace from the computer command prompt to the target host? Step 8 – Trace a route over the Internet. Task: From a Windows 95/98 or NT workstation that has Internet access click on Start/Programs/MS DOS Command Prompt. An MS-DOS Command Prompt window will open up. Enter tracert www.cisco.com. 7. a. What is the IP address of www.cisco.com? b. How many hops did it take to get to www.cisco.com? If a packet passes through a router it is considered one (1) hop and the TTL of the packet is decremented by one (1). Step 9 - View the routing table of the router. Task: From the router prompt enter show ip route. Explanation: This will show you the router's routing table. 8. List the IP network number addresses that are directly connect to you.