Releasing and Renew IP Address in Kubuntu and Ubuntu

Type the following command
1. sudo /etc/init.d/networking restart
2. sudo dhclient -r
3. sudo dhclient

Internet Systems Consortium DHCP Client V3.1.1
Copyright 2004-2008 Internet Systems Consortium.
All rights reserved.
For info, please visit http://www.isc.org/sw/dhcp/

wmaster0: unknown hardware address type 801
wmaster0: unknown hardware address type 801
Listening on LPF/pan0/62:d0:a5:7a:31:db
Sending on LPF/pan0/62:d0:a5:7a:31:db
Listening on LPF/wmaster0/
Sending on LPF/wmaster0/
Listening on LPF/eth0/00:26:9e:16:41:56
Sending on LPF/eth0/00:26:9e:16:41:56
Listening on LPF/vboxnet0/0a:00:27:00:00:00
Sending on LPF/vboxnet0/0a:00:27:00:00:00
Listening on LPF/wlan0/00:24:d2:ea:d8:48
Sending on LPF/wlan0/00:24:d2:ea:d8:48
Sending on Socket/fallback
DHCPRELEASE on wlan0 to 123.45.67.2 port 67
paul@platform2u:~$ sudo dhclient
Internet Systems Consortium DHCP Client V3.1.1
Copyright 2004-2008 Internet Systems Consortium.
All rights reserved.
For info, please visit http://www.isc.org/sw/dhcp/

wmaster0: unknown hardware address type 801
wmaster0: unknown hardware address type 801
Listening on LPF/pan0/62:d0:a5:7a:31:db
Sending on LPF/pan0/62:d0:a5:7a:31:db
Listening on LPF/wlan0/00:24:d2:ea:d8:48
Sending on LPF/wlan0/00:24:d2:ea:d8:48
Listening on LPF/wmaster0/
Sending on LPF/wmaster0/
Listening on LPF/eth0/00:26:9e:16:41:56
Sending on LPF/eth0/00:26:9e:16:41:56
Listening on LPF/vboxnet0/0a:00:27:00:00:00
Sending on LPF/vboxnet0/0a:00:27:00:00:00
Sending on Socket/fallback
DHCPDISCOVER on wmaster0 to 255.255.255.255 port 67 interval 3
DHCPDISCOVER on vboxnet0 to 255.255.255.255 port 67 interval 7
DHCPDISCOVER on pan0 to 255.255.255.255 port 67 interval 7
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 8
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 8
DHCPDISCOVER on wmaster0 to 255.255.255.255 port 67 interval 8
DHCPDISCOVER on vboxnet0 to 255.255.255.255 port 67 interval 12
DHCPDISCOVER on pan0 to 255.255.255.255 port 67 interval 15
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 14
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 8
DHCPOFFER of 123.45.67.50 from 123.45.67.2
DHCPREQUEST of 123.45.67.50 on wlan0 to 255.255.255.255 port 67
DHCPACK of 123.45.67.50 from 123.45.67.2
bound to 123.45.67.50 -- renewal in 357363 seconds.
paul@platform2u:~$ sudo /etc/init.d/networking restart
* Reconfiguring network interfaces... Ignoring unknown interface wlan0=wlan0.
[ OK ]

*** YOU CAN NOW CONNECT YOU WILRELESS CONNECTION BY RELEASING THE IP. ***