| Lab 9.2.4.1 Show ARP & clear ARP Estimated time: 30 min. Objectives: Become familiar with the router show ARP command. Become familiar with the router clear ARP command. Background: In this lab you will view the ARP table stored in the router and clear the router's ARP table. These two commands are very important in troubleshooting a network problem. The router keeps very detailed information about MAC address and associated IP addresses. From time to time this information can become corrupt and will cause packet delivery problems. When this happens the router ARP table must be cleared and rebuilt. Tools / Preparation: Prior to starting this lab you will need to connect a PC workstation (with the HyperTerminal program loaded) to a router using the router's console interface with a roll-over (console) cable. All lab work is done through the HyperTerminal program that is configured to connect to the router. You should review Semester 2 online curriculum Chapter 9 prior to starting this lab. Work individually or in teams. Be familiar with the following commands: Enable Show arp Clear arp Ping Resources Required: PC connected to the router console port with a roll-over cable. Windows operating system (Win 95, 98, NT or 2000) installed on PC. HyperTerminal program configured for router console access. PC connected to the Router console port with a roll-over cable. 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 - Login to the router. Explanation: Connect to the router and login. Enter the password cisco if prompted. Step 2 - Show the router's ARP table. Task: Enter show arp at the router prompt. Explanation: The router will respond with the ARP table that shows IP address to MAC address to interface number. 1. What three (3) important pieces of information are displayed? Step 3 - Enter privileged mode. Task: a. Enter enable at the command prompt. b. Enter the password of class. Explanation: You use the enable command to enter privileged EXEC mode. Step 4 - Enter the help command. Task: Enter the help command by typing ? at the router prompt. Explanation: The router responds with all commands available in Privileged-Mode. 2 a. What is the significance of entering ? at the router prompt? 2 b. Does the clear command appear as an option? Step 5 - Clear the ARP table. Task: Enter clear arp command at the router prompt. Explanation: The router will clear the arp table. Step 6 - Show the ARP table. Task: Enter show arp command at the router prompt. Explanation: The router will respond with the ARP table. 3. Are there any entries in the ARP table? 4. Looking at the IP address of the ARP entries what are the entries for? Step 7 - Generate network traffic. Task: Ping all interfaces on the network. Explanation: This will generate network traffic between routers. Step 8 - Show the ARP table. Task: Enter show arp command at the router prompt. Explanation: The router will respond with the ARP table. 5. Are there any new entries in the ARP table? Step 9 - Generate network traffic. Task: Open an MS-DOS command prompt (Start/Programs/MS DOS Command Prompt). Ping all the workstations on the lab network. Note: You will have to make sure that all workstations have proper IP addressing for the network they are connected to and a default gateway. Explanation: This will generate network traffic from workstation to workstation. Step 10 - Show the ARP table. Task: Enter show arp command at the router prompt. Explanation: The router will respond with the ARP table. 6. Are there any new entries in the ARP table? 7. Explain why there were no new entries in step 8 and there are in step 10. Step 11 - Exit the router.