Trusty Tahr

Changing the MAC (Media Access Control) address of NICs (Network Interface Cards)

In some networks, e.g. the one of Helsinki University, computer's have to be registered in order to get connected. Upon registration the computer receives a name and an IP address. Every time it connects to the network, the DHCP server assigns it the same name and IP address. The DHCP server identifies computers based on the MAC address which is unique for every NIC. However, if you know the MAC address of a registered coputer, you can use it to connect to the network faking the MAC address. This is especially easy with Linux computers:
ifconfig eth0 down