wireless interview questions

Top 15 wireless interview questions

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Network service discovery disabled: What does this mean for me?

Every time at boot I get a message “Network service discovery disabled. Your current network has a .local domain, which is not recommended and incompatible with the Avahi network service discovery. The service has been disabled.”

Network service discovery disabled

What does this mean for me?

Wi-Fi is disabled.

Source: (StackOverflow)

How do I connect to a WPA wifi network using the command line?

So basically, I'd like to use iwconfig to connect to my wifi network when I'm not inside X. But I just don't see a way to do it in the man page. Any idea?

Source: (StackOverflow)

How to share a wired Internet connection with an Android phone (reverse-tethering)?

I have been trying to share my wired Internet connection with my Android phone. However I could not succeed in doing this. Has anyone of you ever succeeded? Operating systems that I use are as follows:

  • Ubuntu 10.10
  • Android 2.3

Source: (StackOverflow)

How to set up Ubuntu as wireless accesspoint?

How can I set up my WiFi to be used as wireless access point on Ubuntu Server?

I have a local Ubuntu Server, it has a wireless card in it (802.11a/b/g/n) and I really want to set it up as an 802.11n access point since my normal access point does not support N.

It needs to work as a switch as well so I can connect and get DHPC through.

Edit: I don't see Network Manager as a good solution since it depends on a lot of X11 packages, and i don't want that on a server.

Source: (StackOverflow)

"Starting Wireless Hotspot..." but nothing happens

I was trying to create an WiFi hotspot for my android device. I used ap-hotspot to do so.

I configured the ap-hotspot using

sudo ap-hotspot configure

Then I started ap-hotspot using

sudo ap-hotspot start

Then it shows this

Starting Wireless Hotspot...

And then nothing happens, no further message is displayed, hotspot is not created.

What is Wrong? How to fix it?

Source: (StackOverflow)

A tool to measure signal strength of wireless

I want to know if there exists any command line option or GUI tool (Ubuntu 11.10) so that I can measure the strength of wireless signal at a given location. I have a house where the wireless is not easily accessible at all corners I want to know at which corners or rooms the signal is weak.

Source: (StackOverflow)

How can I adjust the preferred WiFi order? [duplicate]

This question already has an answer here:

I am using 13.04 Ubuntu. I want to make order on multiple wireless access.

Is there any way to do this?

Source: (StackOverflow)

My WiFi adapter is not working at all, how to troubleshoot?

On this site I see hundreds if not a thousand questions being asked about issues with a Wireless LAN adapter not being detected/recognized by Ubuntu. Some mainstream adapters appear to be utterly broken in Linux support, while others just require some simple steps to get it to work.

The options to get it to work appear to be infinitely huge and I have no clue where to get started!

What is considered 'best practice'? What order of things to try is most efficient in terms of time, effort and imposes minimal risk to my Ubuntu installation? Please help me save time and guide me what to do, step by step.

Source: (StackOverflow)

How to set wifi driver settings to prefer 5 GHz channel above 2.4 GHz

Currently I'm in a new building of my university. In this building my wifi often breaks down and then restores connection again. This is really irritating since it happens a lot.

Now as a coincidence there were some tech guys running around here and where asking everyone if the wifi was doing fine. I told them that my wifi tears down all the time and then reconnects. They figured out that my wifi is switching all the time between the 2.4 GHz channel and 5 GHz channel. They asked me if I could acces the driver settings of my wireless card. Unfortunately I don't know how to do this is in either Linux or Windows. And unfortunately again they only knew the windows solution xD.

So I hope somebody can tell me how I tell my wifi that it should stay on the 5 GHz network and not disconnect and switch to the 2.4 GHz channel?


@arhimed, firstly thank you for your help.

I just tried what you said. It is some what different for me. I can't seem to save the settings when I change the setting and choose to use only the 5 GHz band.

"Network connections"->"Select the appropriate wireless network and click edit"->"In the wireless tab"->"Change the mode from infrastructure to ad-hoc"->"Choose 5 GHz band"

Wireless connection settings panel

However when I want to change the mode from infrastructure to ad-hoc the "save" button tells me that I have to authenticate myself. However I get no pop-up asking me for a password. Using sudo gnome-control-center didn't help either. I could still not save it. Also a error occured then in the terminal:

** (nm-connection-editor:5577): WARNING **: Invalid setting Wireless Security: Security not compatible with Ad-Hoc mode

Hopefully this is some usefull info for you to help me further.

--edit 2012/09/07-- Still no answer... Anyone?

Source: (StackOverflow)

Wireless card Realtek RTL8723AE-BT is not recognized

I bought a new laptop with a RTL8723AE-BT wireless card, but it seems there is nothing that makes it work.

Realtek usually makes drivers available for its card, but this specific one doesn't have a driver available on Realtek's website. I have tried the following steps in order to try and make it work:

  1. Installed ndiswrapper versions 1.57 (from repositories, with dkms) and 1.58rc1 (compiled from source from ndiswrapper's website). Both failed: version 1.57 does not provide an interface for the functions IoWMIOpenBlock and IoWMIQueryAllData. 1.58rc1 has dummy functions in their places, but it fails with a "ioremap failed" message.

    Upon further investigation, I have found that the function NdisMMapIOSpace (ndis.c:808), in 1.58rc1, gets called with physical address and length zero, which causes the failure. Since this function doesn't seem to be called from anywhere in ndiswrapper's code, I'd assume the Windows driver is somehow calling it with bogus parameters.

  2. I tried using both the 64-bit version (on my installed system, which uses the x86_64 version of Ubuntu) and the 32-bit version (on a live-USB x86 system with persistence enabled) of the Windows XP driver. The same errors occurred for both versions.

  3. Since Realtek's Linux drivers for RTL8192CE/SE/DE actually mention the 8723 chipset in its sources, I tried compiling them and modprobing them, but they don't pick up the card ID (10ec:8723). I also tried to echo 10ec 8723 > new_id on the sysfs (/sys/bus/pci/drivers/rtl8192de) location ( of the driver (actually, on each of them, one at a time), but I get a "Permission denied" error even with sudo. If I sudo su and try again, I get the error bash: echo: write error: Invalid argument.

I have run out of ideas. It's really frustrating to buy a new notebook to use only with Ubuntu and not be able to use its wi-fi connection.

If anyone can shed a light on alternatives, I'd be very thankful.

Edit: lshw -C network output

$ sudo lshw -C network -numeric
  *-network UNCLAIMED     
       description: Network controller
       product: Realtek Semiconductor Co., Ltd. [10EC:8723]
       vendor: Realtek Semiconductor Co., Ltd. [10EC]
       physical id: 0
       bus info: pci@0000:03:00.0
       version: 00
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress cap_list
       configuration: latency=0
       resources: ioport:d000(size=256) memory:f7900000-f7903fff
       description: Ethernet interface
       product: RTL8111/8168B PCI Express Gigabit Ethernet controller [10EC:8168]
       vendor: Realtek Semiconductor Co., Ltd. [10EC]
       physical id: 0.2
       bus info: pci@0000:04:00.2
       logical name: eth0
       version: 0a
       serial: 00:90:f5:cd:6d:f7
       size: 100Mbit/s
       capacity: 1Gbit/s
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress msix vpd bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation
       configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=full firmware=N/A ip= latency=0 link=yes multicast=yes port=MII speed=100Mbit/s
       resources: irq:43 ioport:c000(size=256) memory:f2104000-f2104fff memory:f2100000-f2103fff

Source: (StackOverflow)

16.04 LTS wifi connection issues

I discovered several issues with wifi connection after installing 16.04 LTS.

First, wifi doesn't reconnect normally after sleep or hibernation. Sometimes the network icon turns into a "up and down arrows"(I don't know what it is for) after waking up but is still connected. Sometimes network is simply lost and it doesn't display any network in the list so there's simply no way to use wifi at all.

I first tried restarting network manager by running sudo service network-manager restart. It worked but was not a permanent resolution.

Then according to another thread, I added SUSPEND_MODULES="iwlwifi"to


After doing this, the reconnect issue seems to be fixed(can automatically reconnect and icon doesn't change anymore.) However, I find the wifi connection gets lost randomly (about every 30 minutes) even when the computer is running and the network icon remains the connected state when connection is lost.

Another issue after adding the code is, when I put my computer to sleep, the screen will turn off for a second but then turns back on for around 5 seconds(during which the system will cut off wifi connection). And then the computer will go to sleep after this unusual "two-phase" process.

Plz find Wireless Cards info below

       description: Wireless interface
       product: RTL8723BE PCIe Wireless Network Adapter
       vendor: Realtek Semiconductor Co., Ltd.
       physical id: 0
       bus info: pci@0000:02:00.0
       logical name: wlp2s0
       version: 00
       serial: b0:c0:90:5c:1c:d5
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless
       configuration: broadcast=yes driver=rtl8723be driverversion=4.4.0-21-generic firmware=N/A ip= latency=0 link=yes multicast=yes wireless=IEEE 802.11bgn
       resources: irq:16 ioport:d000(size=256) memory:df200000-df203fff

00:00.0 Host bridge: Intel Corporation Sky Lake Host Bridge/DRAM Registers (rev 07)
00:01.0 PCI bridge: Intel Corporation Sky Lake PCIe Controller (x16) (rev 07)
00:02.0 VGA compatible controller: Intel Corporation Sky Lake Integrated Graphics (rev 06)
00:14.0 USB controller: Intel Corporation Sunrise Point-H USB 3.0 xHCI Controller (rev 31)
00:14.2 Signal processing controller: Intel Corporation Sunrise Point-H Thermal subsystem (rev 31)
00:16.0 Communication controller: Intel Corporation Sunrise Point-H CSME HECI #1 (rev 31)
00:17.0 SATA controller: Intel Corporation Sunrise Point-H SATA controller [AHCI mode] (rev 31)
00:1c.0 PCI bridge: Intel Corporation Sunrise Point-H PCI Express Root Port #1 (rev f1)
00:1d.0 PCI bridge: Intel Corporation Sunrise Point-H PCI Express Root Port #9 (rev f1)
00:1f.0 ISA bridge: Intel Corporation Sunrise Point-H LPC Controller (rev 31)
00:1f.2 Memory controller: Intel Corporation Sunrise Point-H PMC (rev 31)
00:1f.3 Audio device: Intel Corporation Sunrise Point-H HD Audio (rev 31)
00:1f.4 SMBus: Intel Corporation Sunrise Point-H SMBus (rev 31)
00:1f.6 Ethernet controller: Intel Corporation Ethernet Connection (2) I219-V (rev 31)
01:00.0 VGA compatible controller: NVIDIA Corporation GK208 [GeForce GT 730] (rev a1)
01:00.1 Audio device: NVIDIA Corporation GK208 HDMI/DP Audio Controller (rev a1)
02:00.0 Network controller: Realtek Semiconductor Co., Ltd. RTL8723BE PCIe Wireless Network Adapter
03:00.0 Non-Volatile memory controller: Samsung Electronics Co Ltd NVMe SSD Controller (rev 01)

05/01/2016 Update: I don't know what happened but the issue gets worse now. Wifi connection gets lost about every 5 minutes and I have to reconnect or restart network-manager.

Source: (StackOverflow)

How to disable built-in wifi and use only USB wifi card?

The built-in wifi card in my laptop (Dell XPS M1330) is crap, pretty much. I have an Asus USB wifi card which is significantly better, and it works fine. What I'd like to do is disable the built-in wifi card. Is there a way to do this (without having to boot into BIOS each time I want to disable/enable the built-in wireless)?

@mikewhatever: Here are those outputs

matt@sbod:~$ lsusb
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 002 Device 002: ID 0b05:179d ASUSTek Computer, Inc. 
Bus 002 Device 004: ID 05a9:2640 OmniVision Technologies, Inc. OV2640 Webcam
Bus 007 Device 002: ID 0483:2016 SGS Thomson Microelectronics Fingerprint Reader
matt@sbod:~$ lspci -nnk | grep -iA2 net
09:00.0 Ethernet controller [0200]: Broadcom Corporation NetLink BCM5906M Fast Ethernet PCI Express [14e4:1713] (rev 02)
    Subsystem: Dell XPS M1330 [1028:0209]
    Kernel driver in use: tg3
0c:00.0 Network controller [0280]: Broadcom Corporation BCM4312 802.11b/g LP-PHY [14e4:4315] (rev 01)
    Subsystem: Dell Wireless 1395 WLAN Mini-Card [1028:000b]
    Kernel driver in use: wl

Source: (StackOverflow)

How can I get Broadcom BCM4311 Wireless working? [duplicate]

This question already has an answer here:

Wireless was worked perfectly in ubuntu 10.10. Now I upgraded it to ubuntu 11.04. After this upgrade wireless is not working in my laptop, even "wireless connection" is not showing in network connection list.

What I have to do for this?

lspci output:

06:00.0 Network controller: Broadcom Corporation BCM4311 802.11b/g WLAN (rev 01)

Source: (StackOverflow)

Ubuntu as Miracast Sender/receiver

couldn't find anything about Ubuntu act as a Miracast receiver or sender.
General info about Miracast at Wikipedia

  • Should this work?
  • Supported HW? (Wifi direct?)
  • only via WiFi no LAN?
  • If Wifi direct works should Miracast just work too?

I plan to use it together with an Android phone (4.x Jelly Bean)

Only hint I found at brainstorm.ubuntu.com/idea/30810 seems dead (well the brainstorm redirect me to the Ubuntu community page. see my other questions:

Source: (StackOverflow)

Wifi doesn't work after suspend after 16.04 upgrade

This particular version of the "doesn't work after suspend" came after upgrading to 16.04. It seems that the upgrade includes a Wicd applet (added to Metacity Classic Gnome task bar alongside regular network icon), but doesn't seem to work after a suspend. A sudo service network-manager restart duplicates this problem. It takes a complete reboot to get Wifi going again. Any ideas why?

Source: (StackOverflow)