Re: NetworkManager with multiple wireless cards

[Dan Williams <dcbw redhat com>]

On Fri, 2008-06-20 at 16:08 +0100, Andrea wrote:
> Hi,
> 
> I have 2 wireless cards on my laptop: Centrino IPW2100 and Broadcom b43.
> 
> I am running Fedora 9, KDE 4.0.5, NM 0.7.0.
> 
> When I select a network from the list of one of the 2 cards, both cards are connected to that network.

Sounds like a bug but only in _some_ cases.  If you lock your
connections down to a specific card (by setting the card's MAC address
in the connection editor), then NM will only use that connection with
that card.  If you don't, and the connection is marked with autoconnect,
then NM will bring that connection up on any wireless card available if
the card can see the AP.  If the connection is not marked autoconnect,
then you can manually tell NM which connection to bring up on which
card.

In the case where you've never connected to the AP before, here's what
happened:

1) You select the AP from the menu
2) The applet creates a new connection for the AP and marks autoconnect
for you
3) The applet tells NM to activate the new connection on the specified
card
4) NM activates the new connection on the specified card
5) since the new connection is _not_ locked to the specific card you
just chose, NM is free to activate that new connection on any given card
that isn't currently connected
6) NM activates that new connection on the second wireless card because
it's not locked to the first card

So if you went into the connection editor and MAC-locked the connection
to the card you want, that would probably solve your problem.

> NM does not report it in the Connection Information, but ifconfig shows that both interfaces are 
> connected.

Do you mean 'iwconfig'?  The SSID shown in iwconfig doesn't necessarily
mean that NM has connected to the AP.  Drivers will sometimes
auto-associate with a given AP (but of course you won't have an IP
address or routes because NM hasn't brought the connection up), other
times there are bugs in the driver that leak an SSID through even when
it's not really connected to the AP.  A real association will have both
a valid BSSID and a valid SSID as reported by 'iwconfig'.

To determine what NM has done, run 'nm-tool' and see what interfaces are
'activated'.

> Moreover, I cannot figure out how to specify the default route.

The default route is either given by DHCP if you are using DHCP, or by
manually configuring the route in the connection editor, or by the last
connection that was activated if there are two devices of the same
class.  So if you have two DHCP-enabled wireless connections, then the
one that was activated last more or less wins the default route.  I'm
looking into how to make this more controllable through metrics for
manual connections, and other methods for DHCP-enabled connections.

> I think the NM should only connect the interface selected and not all of them.

Depends, see the explanation above.

> On top of that, when more that 1 interface is enabled, there should be a way to choose the default 
> route.

Yes, there probably should be a better way than "last one wins".
However, if there were a hypothetical "this connection is always
default", what should happen if you mark two connections as always
default?  last one wins like it currently is?

Dan