> For the complete documentation index, see [llms.txt](https://derek-johnson-1.gitbook.io/welcome/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://derek-johnson-1.gitbook.io/welcome/freshman/network-150/week-4/johnson-3.2-02-05-23.md). # Johnson 3.2 02 05 23 **Objective:** Understand broadcast domains on a layer 2 LAN **Goals:** * Observe and explain the importance of ARP and layer 2 broadcasts * Understand the limitations of layer 2 LANs * Introduce the need for "routing" to connect LANs * Observe the impact on layer 2 headers (MAC Addresses) as packets cross from one LAN to another **Remember, for each lab your tech journal should include:** * *A brief (one sentence) summary describing what you did in the lab.* * *Any commands or instructions that you found useful and will need to use again in the future.* * *Any problems you ran into during the lab, and what troubleshooting steps you took to fix them.* * *Labs will also contain specific items to include or questions to answer within your tech journal. (For this lab, you'll find them at the very end of this document.)* **I. Analyze Traffic to a Remote Network (different LAN)** 1. Open a Command Prompt (windows) or Terminal (Linux) 2. Open wireshark and start a capture 3. Back in the Command Prompt/Terminal- ping the Google Public DNS server (8.8.8.8) 4. Stop Capture 5. **Deliverable 1**: Analyze the ICMP Response from Google: * Answer: What is the source MAC address? What is the destination MAC address? (Hint: Data Link Layer Header) **Source: 00:0c:29:84:a4:ca** **Destination: ec:13:db:c8:8e:81** * * Answer**:** Does the source MAC address look familiar from prior labs? Do you think it is the Google Server's MAC address? 1. **The source is our Virtual Machine’s Mac address and the destination is the Juniper default gateway.** **II. Examine both sides of a ping** 1. Find a partner in class and get their IP address. 2. From your workstation, ping your partner's IP and make sure you get a response 3. On your workstation, start a wireshark capture, ping your partner's IP, and stop the capture 4. On your workstation, analyze the capture * **Deliverable2:** What are the source and destination MACs in the ping reply 5. ![](https://2268061532-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fo71vDQ8YHfe6Cj11Juh6%2Fuploads%2FPi4gIDpEwjKVOrOtUMKW%2F0.png?alt=media) 6. What is your partner's MAC address? * **Deliverable3:** Does the MAC address match the address from you traffic capture? If not - what do you think happened? 7. ![](https://2268061532-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fo71vDQ8YHfe6Cj11Juh6%2Fuploads%2Fibx7EQacOtvcTBKO8P0v%2F1.png?alt=media) * **Yes this is the correct MAC address.** **III: Capture both sides of the ping request** 1. Start a Wireshark capture on both PCs and let it run 2. From a command prompt on your workstation, ping your partner's IP address 3. Stop the captures on both Workstations 4. Find and compare the ICMP traffic on both devices 5. **Deliverable4:** 1. On your workstation**,** what is the source and destination MACs from the pings? 2. ![](https://2268061532-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fo71vDQ8YHfe6Cj11Juh6%2Fuploads%2FDgLMHgKGrww9hjaP8gdf%2F2.png?alt=media) 3. On your partner's workstation**,** what is the source and destination MACs from the pings? 4. **On my partner’s machine they are switched, their destination is my address and their source is their address.** 6. **Deliverable5:** Why do you think they are different? 1. **Because I am sending the ping request from my machine and my partner is sending the ping request from theirs.** ### Tech Journal **Deliverable 6:** Add link to typed up tech journal notes. * Make sure you understand ARP * Make sure you know how to capture a packet and how to look through network traffic.