Technical Interview Scenario: Troubleshooting Network Issues
Introduction
Rob:
Scenario
💻 For this scenario, let's say that you're working help desk for a global company. You get a call first thing in the morning from a user in a remote office, they sound panicked and they tell you that the network is down in their office. ☎️
User's Symptoms
😟 What do you do?
🤓 I will assure the user that I'll be able to help them out, and then I will also want to know the network outage symptom. Are you receiving an error message?
💻 Let's say that I just opened up my laptop and I tried to access one of our internal websites, I get an error message and it says page can't be displayed.
❓ Okay. Do you know of any other users are having this issue?
🤷 No, I'm not sure. It's first thing in the morning, and I'm the first one here.
🔍 Okay. Can you actually give me the name of the website, I'd like to test that on my computer.
💻 Sure. The URL for the internal website is intranet.companyx.com.
👍 Okay, thanks. I'm going to test that out.
💻 All right. Let's say that it loads up fine just for you. Okay. Now I want you try out external website, so maybe try Google.com.
😦 I get the same result on Google.com, page can't be displayed.
Troubleshooting Steps
🤔 Okay. What OS are you using?
💻 Let's say I'm using Windows 7.
⌨️ I want you to navigate to command prompt. The way you could do that is just going to Start menu and search CMD.
💻 Let's say I launch that, I have my black command prompt window open. Now, can you run the command ipconfig/all.
🔍 I do that and I see a bunch of things. I see IP address, default gateway, DNS, and I'm a curious user. Can you explain to me what all those things mean?
🤓 Yes. IP address is a unique numerical address given to computing devices to communicate on the Internet to other computers. Default gateway serves as an access point that's used by computers to send information to another computer or on the Internet. That can be a router. DNS is domain name system, so that translate domain names into IP addresses.
:light_bulb: Great. Let's say I read you all this info and I tell you my IP address is 192.something.something. But you know that our network only uses addresses in the range of 172.something.something. Does that mean anything?
🤔 Yeah. Does this machine use DHCP?
💻 It does. But since you brought that up, can you explain to me what DHCP is?
🤓 Yes. Dynamic Host Configuration Protocol automatically assigns IP addresses to computing devices, and it can also send network configurations too.
❓ Why would that be important in this scenario?
💡 This will be important just because if the IP addresses getting assigned statically, then we have to go in and change it, but it should be in the site automatically.
:back_to_top: Back to our scenario. What are some reasons I might be getting the wrong IP address from DHCP?
🤔 DHCP can be configured incorrectly, or you could be connected to the wrong network. Let's start with the more simple explanation. How can we check what network I'm connected to? Do you know if you're connected to wired or wireless network?
💻 I'm on my laptop, so I'm on wireless.
🔍 If you're on wireless, let's go to the bottom-right corner and click on the Wi-Fi symbol, and then go into network preferences just to see what network you're actually connected to.
💻 When I do that, you're right, I'm connecting to some random network across the street. Once I switch back to our corporate wireless, it seems to solve the issue.
👍 I guess the network wasn't down after all. Good job.
Conclusion
🎓 In this scenario, we saw a great example of asking clarifying questions. Problem started with the user saying that the network was down. That can actually mean many things. It's important to figure out what exactly is going wrong before we start trying to fix things. We also saw a few examples of having to explain the terms we use during the interview. If you use a term like DNS or DHCP, it's important that you know what it means and how it might be relevant. 👏
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