Hello,
My interfaces file looks like this

auto
lo
iface lo inet loopback

auto eth0
iface eth0 inet static
address 192.168.2.4
netmask 255.255.255.0
gateway 192.168.2.1

auto wlan0
iface wlan0 inet dhcp

1 I connect the net cable and boot the computer,
I have network connection, I can ping 192.168.2.1 and I can connect to
the internet.

2 I disconnect the net cable and sudo /etc/init.d/networking restart
the system tells me that it receives a dhcp offer and got ip
192.168.2.5 for wlan0(the wireless card). After this, I try to ping
192.168.2.1(the router), I got unreachable
message. and it shows that my ip is still 192.168.2.4(static ip of
eth0).

3 I sudo ifdown eth0
and everything is ok, I can ping 192.168.2.1 and I can connect to the
internect.


What confuses me is that why do I have to ifdown eth0 to change the
computer ip to the wireless ip?

Thanks.
Zhengquan

On 2008-06-30, zhengquan <zhang.zhengquan@gmail.com> wrote:
>
>
> Hello,
> My interfaces file looks like this
>
> auto
> lo
> iface lo inet loopback
>
> auto eth0
> iface eth0 inet static
> address 192.168.2.4
> netmask 255.255.255.0
> gateway 192.168.2.1
>
> auto wlan0
> iface wlan0 inet dhcp
>
> 1 I connect the net cable and boot the computer,
> I have network connection, I can ping 192.168.2.1 and I can connect to
> the internet.
>
> 2 I disconnect the net cable and sudo /etc/init.d/networking restart
> the system tells me that it receives a dhcp offer and got ip
> 192.168.2.5 for wlan0(the wireless card). After this, I try to ping
> 192.168.2.1(the router), I got unreachable
> message. and it shows that my ip is still 192.168.2.4(static ip of
> eth0).
>
> 3 I sudo ifdown eth0
> and everything is ok, I can ping 192.168.2.1 and I can connect to the
> internect.
>
>
> What confuses me is that why do I have to ifdown eth0 to change the
> computer ip to the wireless ip?
>
I think the problem is that you are trying to use two addresses in the
same subnet.