IPv4 address shortage
The long term solution is to switch to Internet Protocol version 6 (IPv6). IPv6 has trillions of trillions of addresses, enough to give every computer in the world a unique IP address. Unfortunately, IPv6 is mostly incompatible with IPv4, and implementing it often requires replacing equipment such as routers. Not all ISPs currently offer IPv6. There are several backward compatibility protocols such as Protocol 41 and Teredo that allow a computer with only an IPv4 address to obtain an IPv6 address.