I have installed the Ubuntu 14.04 on Dell Vostro 2520 laptop. Wifi is not working after installation. Tried several methods to install but nothing happens. Vostro-2520:~$ sudo rfkill list all 0: hci0: Bluetooth Soft blocked: no Hard blocked: no Vostro-2520:~$ iwconfig usb0 no wireless extensions. eth0 no wireless extensions. lo no wireless extensions. The hardware is Broadcom 802.11 bcm43142. Please help to solve this issue.