wiskas@zohar:~$ sudo aptitude -t experimental install ifupdown
.....
#OK
wiskas@zohar:~$ sudo ifdown wlan0
interface-down wlan0
Error for wireless request "Set Mode" (8B06) :
    SET failed on device wlan0 ; Invalid argument.
wiskas@zohar:~$ sudo ifup wlan0
RTNETLINK answers: File exists
Failed to bring up wlan0.
wiskas@zohar:~$ sudo ip route
wiskas@zohar:~$ sudo ip link
1: lo: <LOOPBACK,UP,10000> mtu 16436 qdisc noqueue
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop qlen 1000
    link/ether 00:03:0d:53:dd:52 brd ff:ff:ff:ff:ff:ff
3: wmaster0_rename: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast qlen 1000
    link/ieee802.11 00:18:de:35:50:c6 brd ff:ff:ff:ff:ff:ff
4: wlan0: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:18:de:35:50:c6 brd ff:ff:ff:ff:ff:ff
wiskas@zohar:~$ sudo ip addr
1: lo: <LOOPBACK,UP,10000> mtu 16436 qdisc noqueue
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
2: eth0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop qlen 1000
    link/ether 00:03:0d:53:dd:52 brd ff:ff:ff:ff:ff:ff
3: wmaster0_rename: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast qlen 1000
    link/ieee802.11 00:18:de:35:50:c6 brd ff:ff:ff:ff:ff:ff
4: wlan0: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:18:de:35:50:c6 brd ff:ff:ff:ff:ff:ff
    inet 192.168.0.1/24 brd 192.168.0.255 scope global wlan0
    inet 192.168.0.1/32 brd 192.168.0.255 scope global wlan0
wiskas@zohar:~$ sudo ip route add default via 192.168.0.254
RTNETLINK answers: Network is unreachable
wiskas@zohar:~$ sudo ip link set wlan0 up
wiskas@zohar:~$ sudo ip route add default via 192.168.0.254
wiskas@zohar:~$ sudo ifup wlan0
RTNETLINK answers: File exists
Failed to bring up wlan0.
wiskas@zohar:~$ sudo ifdown wlan0
ifdown: interface wlan0 not configured