CCNA Lab 1.2.3 Mapping ISP Connectivity Using Traceroute

Step 1: Run the tracert utility from a host computer
a. Verify that the host computer has a connection to the Internet.

b. Open a Command Prompt window by clicking Start > Run and typing cmd. Alternatively, you may click Start > All programs > Accessories > Command Prompt.

c. At the prompt, type tracert and your first destination website.d.

d. Save the tracert output in a text file as follows:
1) Right-click the title bar of the Command Prompt window and choose Edit > Select All.
2) Right-click the title bar of the Command Prompt window again and choose Edit > Copy.
3) Open the Windows Notepad program: Start > All Programs > Accessories > Notepad.
4) To paste the output into Notepad, choose Edit > Paste.
5) Choose File > Save As and save the Notepad file to your desktop as tracert1.txt.

e. Run tracert for each destination website and save the output in sequentially numbered files.

f. Run tracert from a different computer network, for example, from the public library or from a friend’s computer that accesses the Internet using a different ISP (for instance, cable instead of DSL). Save a copy of that output in Notepad and print it out for later reference.

Step 2: Interpret tracert outputs to determine ISP connectivity
Routes traced may go through many hops and a number of different ISPs depending on the size of your ISP and the location of the source and destination hosts. In the example output shown below, the tracert packets travel from the source PC to the local router default gateway to the ISPs Point of Presence (POP) router and then to an Internet Exchange Point (IXP). From there they pass through two Tier 2 ISP routers and then though several Tier 1 ISP routers as they move across the Internet backbone. When they leave the Tier 1 ISPs backbone, they move through another Tier 2 ISP on the way to the destination server at

a. Open the first traceroute output file and answer the following questions.
1) What is the IP address of your local POP router?….. (      )
2) How many hops did the traceroute packet take on its journey from the host computer to the destination?….. (       )
3) How many different ISPs did the traceroute packet pass through on its journey from the host computer to the destination?….. (       )
4) List the IP addresses and URLs of all the devices in the traceroute output in the order that they appear on the Routes Traced worksheet.5) In the Network Owner column of the worksheet, identify which ISP owns each router. If the router belongs to your LAN, write “LAN”. The last two parts of the URL indicates the ISP name. For example, a router that has “” in its URL belongs to the network of an ISP called Sprint.
6) Did the traceroute pass through an unidentified router between two ISPs? This might be an IXP. Run the whois command utility or whois function of a visual traceroute program to identify ownership of that router. Alternatively, go to to determine to whom the IP is assigned.

b. Complete the worksheet using the traceroute output file for each of the other destination URLs. c. Compare your results from the different traceroute output files. Did your ISP connect to different ISPs to reach different destinations?….. (     )

d. If you ran a traceroute from a different computer network, check the output for that traceroute file as well. Was the number of hops different to reach the same destination from different local ISPs? Which ISP was able to reach the destination in fewer hops?….. (     )

Step 3: Map the connectivity of your ISP
a. For each traceroute output, draw a diagram on a separate sheet of paper showing how your local ISP interconnects with other ISPs to reach the destination URL, as follows:
1) Show all of the devices in sequence from the LAN router to the destination website server. Label all of the devices with their IP addresses.                                                              2) Draw a box around the local POP router that you identified, and label the box “POP”.
3) Draw an ISP cloud around all the routers that belong to each ISP, and label the cloud with the ISP name.
4) Draw a box around any IXP routers that you identified, and label the box “IXP”.

b. Use the Global Connectivity Map to create a combined drawing showing only ISP clouds and IXP boxes.


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