| 4.2 |  | Getting Information about Remote Devices |
| 4.2.5 |  | Alternative connectivity tests |

| As an aid to diagnosing basic network connectivity, many network protocols support an echo protocol. Echo protocols are used to test whether protocol packets are being routed. The ping command sends a packet to the destination host and then waits for a reply packet from that host. Results from this echo protocol can help evaluate the path-to-host reliability, delays over the path, and whether the host can be reached or is functioning. This is a basic testing mechanism. This operation can be performed at either the user or privileged EXEC modes. The ping target 172.16.1.5 in Figure responded successfully to all five datagrams sent. The exclamation points (!) indicate each successful echo. If one or more periods (.) are received instead of exclamations on the display, the application on the router timed out waiting for a given packet echo from the ping target. The ping user EXEC command can be used to diagnose basic network connectivity. The command p ing uses ICMP (Internet Control Message Protocol). The traceroute command is the ideal tool for finding where data is being sent in a network. The traceroute command is similar to the ping command, except that instead of testing end-to-end connectivity, traceroute tests each step along the way. This operation can be performed at either the user or privileged EXEC levels. In this example, the path from York to Rome is being traced. Along the way the path must go through London and Paris. If one of these routers is unreachable, three asterisks (*) will be returned instead of the name of the router. The traceroute command will continue attempting to reach the next step until the Ctrl-Shift-6 escape sequence is used. A basic verification test also focuses on the network layer. Use the show ip route command to determine whether a routing table entry exists for the target network. This command will be discussed in more detail in a later module of this course. The procedure to use the ping command is as follows: ping IP address or name of destination press the Enter key The procedure to use the traceroute command is as follows: traceroute IP address or name of destination press the Enter key
| Lab Activity Lab Exercise: Connectivity Tests – Ping In this lab, the students will use the ping command to send ICMP datagrams to a target host.
| Lab Activity Lab Exercise: Connectivity Tests – Traceroute In this lab, the student will use the traceroute command to determine the path from a source to a destination.
| Lab Activity e-Lab Activity: Alternate Connectivity Tests – Ping In this lab, the students will use the ping command to send ICMP datagrams to a target host and using the information retrieved, accomplish the tasks.