wireless-networking interview questions

Top wireless-networking frequently asked interview questions

How to find a router at an unknown location in a house?

I want to install a WLAN repeater in my father’s holiday house which he rents out to other people.

My father is a digital neanderthal and doesn’t know where his router is, therefore I cannot configure my repeater to this router.

Are there any tools that could help me find that router in the house? I know that there are tools that tell you which Ethernet cable is in use and where it points to, so I figured maybe there are tools that help me find my router?

By “tools,” I don’t necessarely mean software, I’m also thinking about a hardware tool. I tried just going around with my cellphone and searching in the area with the best connection to the network but didn’t find the router.

Edit: Due to some comments that wanted more information about the router: It's a normal ADSL/VDSL router which sends WiFi signals. Distributed by the market leader ISP in my country. It also can do WPS. Here's a link:

Update: I came to the conclusion that it's absolutely not possible to find the router, even though I didn't try the kids trick yet, as raystafarian says, you should only use previously known children and I don't know that many children ;-). The woman who cleans the house said she never saw anything like a router there and the Wifi Analyzer App told me it's most likely inside the wall. Nevertheless it's a great tool and I will accept it as an answer. We're now installing a new router and if, one day, we're able to find the mysterious router location, I'll let you guys know. Cheers!

Source: (StackOverflow)

How much Wi-Fi signal strength do I lose per foot of antenna cable?

I'm thinking of buying an antenna for a router so I can extend my Wi-Fi. I have seen a few products like TP-Link TL-ANT2405C Indoor Desktop Omni-directional Antenna:

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The length of the wire is 130 cm. Is it OK if I increase the length of the wire or will it affect the performance of the router? What is the maximum cm of length that I can increase?

Source: (StackOverflow)

Can I make two wireless routers communicate using the wireless?

I want to make a setup like this:

cable modem <-cable-> wireless router 1 <-wireless-> wireless router 2 in another room <-cables-> PCs in another room

Basically, I want to extend my network access across the house and then have a bunch of network jacks available for my office PCs.

Right now, I have a cable modem going to a wireless router in one room and a PC with a wireless PCI card in it in the office on the other side of the house. I use internet connection sharing with the other PCs in the office. The problem is that ICS is flaky, especially when I switch to VPN on the Windows box to access files at work. I picked up a wireless USB adapter that I thought I could share among the PCs I work on but I'm not very happy with it so I'm going to return it (NDISwrapper support for it is poor).

Is this possible? My wireless experience so far has been pretty straightforward so I have no idea what kind of hardware is available. I've looked at network extenders but those just look like repeaters for signal strength. I want wired network jacks in my office.

Source: (StackOverflow)

How do I diagnose and visualize high ping times to wifi router?

I'm seeing erratic and sometimes very long ping times to my wifi router that's just one hop away. Pinging sometimes gives stretches of 400-800ms latencies.

There are plenty of things to try (firmware, router placement, AP channel, etc.), but I would like to attack this problem a bit more methodically:

  • First, how can I visualize the performance of my network?
  • Then, how can I benchmark the performance of a given configuration, so that I can compare reliably after making adjustments?

Source: (StackOverflow)

How to launch a command on network connection/disconnection?

I have a wifi connection that requires to authenticate using a web form once the wireless link is established. I know how to automate the authentication with a script that uses curl/curlIE.

But how can I ask Windows to call my script every time I connect to a particular network connection?

I would be also interested in receiving the name of the wireless profile or the ESSID on the command-line of my script.

Source: (StackOverflow)

How can I get the same SSID for multiple access points?

I need to upgrade my existing wireless infrastructure and this time I want 2 access points to cover my house, since I get blind spots no matter what with a single AP. I have physical cabling to my central network available for both access points.

I would really like these two to interoperate seamlessly as a single SSID. How do I do this? What are the features that the new access points I'm buying would need to support?

Source: (StackOverflow)

Which routers do you prefer for DD-WRT or OpenWRT? [closed]

I'm aware of the giant Supported Devices list. I'm wondering which ones you all prefer (e.g., support for Mega install, cheap, reliable hardware, USB port, etc.)

I've used an ASUS WL-500G Premium for 1.5 years, but I've been eyeballing the WL-520gU recently.

Source: (StackOverflow)

How do I set my wireless network to be private instead of public?

Trying to maintain good security settings on my laptop, I want my home network to be interpreted as private and the university network at school to be interpreted as public. However, my home network is currently showing as public.

Here is what my Network and Sharing Center looks like:

How do I change my home network from public to private on Windows 8 Consumer Preview?

Source: (StackOverflow)

What does the "Fi" in "Wi-Fi" mean?

I just got into a heated discussion about Wi-Fi. What does the Fi in Wi-Fi mean? I would have thought potentially "frequency interface" since all network adapters are classified as interfaces. However I'm not certain.

Source: (StackOverflow)

Display list of computers on a LAN in Linux

I'm a web dev who is trying to get a better handle on security. I'm trying to figure out a way (on Linux/Debian based distros) to list all computers on the same LAN my netbook is on. I tried "arp -n" but I don't feel it's a complete list, as my iPhone is on the same wi-fi router as my netbook, and that didn't come up. Is there some better way to get a full list of machines that are all sharing the same gateway?

Source: (StackOverflow)

How does Google Chromecast connect to secured wifi?

Google Chromecast can be set up by going to the setup page on a supported device. But in technical terms, what is actually happening on your device that configures the Chromecast dongle? For instance, if I have a WPA secured wireless AP, how does the dongle "listen" for configuration information?

afaik the only automatic way of doing this is Wi-Fi Protected Setup (WPS). However, that wouldn't require an additional device. So it seems like Google is doing something else.

Source: (StackOverflow)

How does Windows know whether it has internet access or if a Wi-Fi connection requires in-browser authentication?

In Windows 7, the notification area networking icon will show an error indicator if there is no internet access wifi-err, and the error icon goes away once there is a successful connection to the internet networking normal. Sometimes, if the WiFi connection requires an in-browser authentication step, like on many guest networks in hotels or universities, then the following pop-up bubble appears, saying as much: additional log on information may be required, click to open your browser

How does Windows know whether or not it has a successful internet connection?
Presumably it is checking some online Microsoft service to see whether it has a successful connection, gets redirected to some other page, or doesn't get any response at all, but I haven't seen anywhere that this process or the services used are documented. Can anybody explain how this works? I would prefer answers that refer to facts, rather than just guessing, but if you have a really good guess, then go for it.

This question was a Super User Question of the Week.
Read the May 16th, 2011 blog entry for more details or submit your own Question of the Week.

Source: (StackOverflow)

What is a "Magic Packet" for waking a computer?

My wireless adapter (Intel Dual Band Wireless-N 7260) has two settings in Device Manager which I cannot explain.

Wireless adapter properties

Wake on Magic Packet
Wake on Pattern Match

After a bit of research, I found this Microsoft Technet article which defines the feature as follows:

Defines if a network adapter is enabled to wake a computer on the magic packet.

This rather cryptic description is a bit low on details. Can anyone help?

I would prefer that my laptop not be woken up remotely under any circumstances. I've disabled Allow this device to wake the computer on the Power Management tab, but these settings appear to be separate. My assumption is that I can set these two settings to Disabled without negative consequences. Is that right?

Source: (StackOverflow)

Make Windows 7 ignore WiFi when ethernet is available

When I dock my Windows 7 laptop, I want it to prefer the wired ethernet connection over WiFi.

This is a pretty straightforward thing to do on my Mac - I just reorder my network preferences, and it "does the right thing." I just can't figure out how to achieve the same thing on my Win7 laptop.

So, when I'm docked, it connects to WiFi, and then fails to connect to servers on the local wired network. How do I fix this?

Source: (StackOverflow)

Is it really possible for most enthusiasts to crack people's Wi-Fi networks?

Can most enthusiastic users (even if they are not professionals) use well-known techniques to break through the average home router's security?

Some basic security options are:

  • strong network password with various encryption methods
  • custom router access password
  • WPS
  • no SSID broadcast
  • MAC address filtering

Are some of these compromised and what to do to make the home network more secure?

Source: (StackOverflow)