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#1 2014-04-07 20:29:43

TheAtomicGoose
Member
Registered: 2014-03-29
Posts: 61

How to specify which of 2 wifi cards to use

Hi All,
I recently installed Arch Linux on a USB (not live, a persistant installation). I have 2 wifi cards: one that came with the laptop and is used via PCIe, which is an Intel Centrino Wireless-N 2200. It's awful. The other, which is a USB wifi card and which I want to use, is an ASUS USB-N10. I checked linux-wless.passys.nl to see if the N10 was supported, and it said it was, and also said: "Supported by the rtl8192su and r8712u staging drivers in the mainline Linux kernel. Firmware from userspace is required." I can't get wifi working properly in Arch Linux, which makes it impossible to progress because I can't install anything and am stuck in just using terminal. I don't know how to specify which card to use in Arch. Any help would be much appreciated.
Thank you for your answers in advance!

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#2 2014-04-07 20:32:55

Inxsible
Forum Fellow
From: Chicago
Registered: 2008-06-09
Posts: 9,183

Re: How to specify which of 2 wifi cards to use

create a netctl conf file and explicitly tell it which one to use.

ip addr

should tell you the names of the interfaces (in case you are using predictive interface naming -- it might not be as simple as wlan0 & wlan1)
look at the /etc/netctl/examples/wireless-* configs based on whether you use a wpa or a wep or an open network.


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#3 2014-04-07 20:43:10

TheAtomicGoose
Member
Registered: 2014-03-29
Posts: 61

Re: How to specify which of 2 wifi cards to use

After running ip addr, it doesn't display names for the different devices in a way that I can tell which ones they are. The names that it gave me are: "lo", "enp3s0", "wlp4s0", and "wlp0s20u2". I know that 2 of those are virtual ports for wireless devices that aren't being used, but I don't know how to differentiate.

EDIT: Also, when I try to navigate to etc/netctl/examples/wireless-wpa, it says "Correcting wireless-wpa to ."

EDIT 2: "lo" seems to be a generic interface, and I've narrowed down the names so now I know that my two wireless cards are 'wlp4s0" and "wlp0s20u2". When I ran iwconfig, I got

wlp4s0    IEEE 802.11bgn ESSID:off/any
              Mode:Managed Access Point: Not-Associated Tx-Power=15dBm
              Retry long limit:7 RTS thr:off Fragment thr:off
              Encryption key: off
              Power Management: off

wlp0s20u2 unassociated Nickname:"rtl_wifi"
                Mode:Auto Access Point: Not-Associated Sensitivity: 0/0
                Retry:of RTS thr:off Fragment thr:off
                Encryption key:off
                Power Management:off
                Link Quality:0 Signal level:0 Noise level:0
                Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
                Tx excessive retries:0 Invalid misc:0 Missed beacon:0
lo             no wireless exentions

enp3s0     no wireless extensions

I'm assuming that this means that the latter two interfaces are the unused virtual interfaces. Does this tell you anything important?

Last edited by TheAtomicGoose (2014-04-07 21:05:28)

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#4 2014-04-07 21:03:28

Inxsible
Forum Fellow
From: Chicago
Registered: 2008-06-09
Posts: 9,183

Re: How to specify which of 2 wifi cards to use

Here's an idea,

unplug the USB wifi, run the ip addr command. note down the wireless interface name. Plug in your USB wifi and re run the command. Compare your note. The one that is not on your note will be the USB wifi interface name.

Something tells me it is wlp0s20u2.

Also what do you mean navigate? just doing an ls on it gives you the "Correcting wireless-wpa to ."  -- I am not even sure what that means.


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#5 2014-04-07 21:12:00

TheAtomicGoose
Member
Registered: 2014-03-29
Posts: 61

Re: How to specify which of 2 wifi cards to use

I tried the unplugging it and doing the ip addr command, and you were correct. It is wlp0s20u2. What I mean is that when I navigated to the directory etc/netctl/examples/ and then tried to cd from there to etc/netctl/examples/wireless-wpa/, The terminal returned "Correcting wireless-wpa to ." I'm not just typing that period. That is part of what is returned. As far as I can tell, nothing happens, and I stay in the same directory.

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#6 2014-04-07 21:17:37

TheAtomicGoose
Member
Registered: 2014-03-29
Posts: 61

Re: How to specify which of 2 wifi cards to use

I got my internet working...Thank you so much! You've achieved lifesaver status.

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#7 2014-04-07 21:25:57

Inxsible
Forum Fellow
From: Chicago
Registered: 2008-06-09
Posts: 9,183

Re: How to specify which of 2 wifi cards to use

TheAtomicGoose wrote:

I tried the unplugging it and doing the ip addr command, and you were correct. It is wlp0s20u2. What I mean is that when I navigated to the directory etc/netctl/examples/ and then tried to cd from there to etc/netctl/examples/wireless-wpa/, The terminal returned "Correcting wireless-wpa to ." I'm not just typing that period. That is part of what is returned. As far as I can tell, nothing happens, and I stay in the same directory.

yeah because wireless-wpa is not a directory but a file. I am not sure why it would give that message though.

Glad you got it working. Please mark your thread as solved by editing your first post and appending [SOLVED] to the thread title.


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#8 2014-04-08 02:24:47

TheAtomicGoose
Member
Registered: 2014-03-29
Posts: 61

Re: How to specify which of 2 wifi cards to use

It's now somewhat un-solved, as I went home, changed to a different network, and now my USB wifi card is called wlp0s20u1 instead of wlp0s20u2. Also, when I try to connect to the internet, it works, but when I try to use ping:

1 root@archiso ~ # ping -c 3 www.google.com
PING www.google.com (74.125.226.209) 56(84) bytes of data.

--- www.google.com ping statistics ---
3 packets transmitted, 0 recieved, 100% packet loss, time 2008ms                                     :(

I'm not sure why it would now not be working or why the name of the device would change. Any thoughts?

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#9 2014-04-08 02:51:16

Inxsible
Forum Fellow
From: Chicago
Registered: 2008-06-09
Posts: 9,183

Re: How to specify which of 2 wifi cards to use

Check your logs. It should tell you what happened.


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#10 2014-04-08 04:00:10

Trilby
Inspector Parrot
Registered: 2011-11-29
Posts: 29,442
Website

Re: How to specify which of 2 wifi cards to use

TheAtomicGoose wrote:

I'm not sure why ... the name of the device would change. Any thoughts?

Did you plug it in to a different usb port?  This is a relatively new nameing scheme which was intended to be "predictable", though it is predictable from a hardware standpoint.  Harware that is in the same place on the main board should always have the same name.  Of course then with a usb, if it plugs into a different hub or port, then you can expect it to change names.

Also on the connection error issue - while I personally don't use the netctl style tools (too much automation confuses me, ironic I know) - if ping is even able to attempt to ping "google.com" then you must at least be connected to the router.  Are you sure that router/access point has a working internet connection?

Last edited by Trilby (2014-04-08 04:02:52)


"UNIX is simple and coherent..." - Dennis Ritchie, "GNU's Not UNIX" -  Richard Stallman

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#11 2014-04-08 20:33:20

TheAtomicGoose
Member
Registered: 2014-03-29
Posts: 61

Re: How to specify which of 2 wifi cards to use

@Inxsible: I will, and will get those posted once I have access to 2 computers so that I can use Arch and use a browser at the same time.

@Trilby: Oh, that would definitely explain the differently named device. It definitely has a working internet connection, because when I'm booted into Windows, my internet works perfectly.

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#12 2014-04-08 20:59:22

tomk
Forum Fellow
From: Ireland
Registered: 2004-07-21
Posts: 9,839

Re: How to specify which of 2 wifi cards to use

As you don't want to use the Intel card, blacklist its driver. Also, you can revert to legacy device naming (wlan0 in this case) by disabling the udev rules that implement the new naming scheme that is not working for you.

Details of both these procedures are available in the relevant man and/or wiki pages.

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