Why does one interface interfere with another?

Joshua Judson Rosen rozzin at geekspace.com
Mon Jun 21 10:01:24 EDT 2010


"Greg Rundlett (freephile)" <greg at freephile.com> writes:
>
> I have a system with two physical network interfaces; a cat45 ethernet port
> and a wireless card - otherwise known as any normal computer.
> 
> I configured the wired interface (eth0) to be static by editing /etc/network/
> interfaces (see bottom) and I let the network-manager applet handle the
> networking system, making my wireless interface address governed by DHCP.
> 
> When the wired port has no connection (because I connect the cable to another
> system), the wireless gets all confused and doesn't connect.  Sometimes it
> doesn't even show my wireless network (causing me to blame the Netgear
> wireless router and reboot the wireless router.)  Trying a ping to the router,
> it tries to go through the wired address.

Yes--you're telling the system to always bring up eth0 at boot,
and to set your default gateway to something out through eth0.

> This happens even if there is NO wired connection from the time of
> boot.

You're asking for this by specifying "auto".

It sounds like you want to use "allow-hotplug" and *not* "auto";
then you can have have network-manager or ifplugd manage the interface
exclusively, sense whether there's a cable attached, and automatically
ifup/ifdown the device when you connect/disconnect the cable.

-- 
"Don't be afraid to ask (λf.((λx.xx) (λr.f(rr))))."



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