Re: Ad-hoc network: cannot ping other machine

[Dan Williams <dcbw redhat com>]

On Sat, 2011-10-08 at 23:54 -0500, Patrick McMunn wrote:
> I just wanted to let anyone who runs across this know that I was able
> to resolve the issue. I checked the output of dmesg on the laptop, and
> I saw a message "disassociating by local choice (reason=3)" After
> doing a Google search and finding this was a widely reported problem,
> some of the proposed solutions included disabling power management on
> the laptop's wifi card, disabling wpa_supplicant, and changing the
> channel the connection is using. I was unable to disable
> wpa_supplicant. If I killed the process, it respawned. If I
> uninstalled wpa_supplicant completely, NetworkManager refused to work
> at all. I ended up manually specifying the connection to use channel
> 10 as one person recommended, and voila! I was able to connect, and
> each machine was able to ping the other. Now if I can just get
> internet connection sharing working....

NM uses wpa_supplicant for wifi control, so yeah, you'd need it.  WRT
channel 10 vs. channel 3, that's very interesting; it could be that the
driver for your wifi card is somewhat stupid; I've noticed a lot of
variability in the quality of Ad-Hoc mode support in kernel wifi
drivers.  For example, in certain kernel versions Ad-Hoc + WPA simply
doesn't work.  At all.  But we'd do best to investigate deeper into the
kernel driver here.

Second, for ICS, you want to choose "Shared to other computers" as the
IPv4 connection  method in the Ad-Hoc network you're creating.  If
that's an option in the KDE network config (that appears to be what
you're using...).  The method "Link-Local" will only do Link-local, it
won't start up ICS.

Dan

> On 10/8/11, Patrick McMunn <doctorwhoguy gmail com> wrote:
> > I'm using NetworkManager 0.9.1.90 (just installed yesterday; I've been
> > using 0.9.0 for a while) and KNetworkManager from git. I have never
> > been able to get a working ad-hoc network between two Linux machines -
> > only when I create it with Windows and connect to it with a Linux
> > machine.
> >
> > Here's my setup in KNetworkManager:
> > SSID: 1337
> > Mode: Ad-Hoc
> > Band: b/g
> > Channel: 3
> > BSSID: <blank>
> > Restrict to Interface: Any
> > Cloned MAC Address: <blank>
> > MTU: Automatic
> >
> > IPv4 Address: Link-Local
> > IPv6 Address: disabled
> >
> > results of route from command line of desktop computer
> >
> > Kerne IP routing table
> > Destination     Gateway         Genmask         Flags Metric Ref
> > Use Iface
> > loopback        *               255.0.0.0       U     0      0        0 lo
> > link-local      *               255.255.0.0     U     2      0        0
> > wlan0
> > 224.0.0.0       *               240.0.0.0       U     0      0        0
> > wlan0
> >
> > Settings are the same on desktop and laptop computers. Link-Local is
> > the only setting that will work at all under IPv4 settings. DHCP
> > results: attempts to connect but fails. I have dhcpcd set to fallback
> > to zeroconf, but that doesn't work with NM. I haven't had any luck
> > with static IPs either.
> >
> > When using Link-Local, however, I can connect to the network easily.
> > Then I can walk over to my laptop, use KNetworkManager's scan feature
> > and identify the essid I created on the desktop. I have to change IPv4
> > settings to Link-Local, but everything else is usually identified
> > correctly. Then I save and can connect - apparently. If I look at the
> > network usage statistics of KNetworkManager, the graph indicates
> > network activity for a few moments at the time I attempt to join the
> > network, but then it goes back to zero never to do anything else. I
> > cannot ping either machine from the other. I have tried this with no
> > encryption at all for troubleshooting and with WPA Personal just to
> > see what would happen - both with the exact same results (when I tried
> > encryption, it even asked for my passphrase before connecting, so that
> > seemed to work).
> >
> > Once I get this solved, I want to be able to share internet connection
> > over wifi.
> >
> > Any ideas what's wrong?
> >
> > --
> > Patrick McMunn
> >
> > - Learn more about the Catholic Faith: http://www.catholic.com/
> > - Pray with the Church: http://www.universalis.com/
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