What makes an internal IP external?

[Jskid]

For many home users when they connect to a home router there computer is assigned an IP address in class C (in the range 192.0.0.0 - 223.255.255.255) but there external IP (issued by the ISP) is different (e.g. 206.87.81.34). What device is responsible for this translation and how does it not which packet to send to which node on the network?

 

[Pan Wah]

The router does it, have a look at this http://www.howstuffworks.com/nat.htm for more detail

 

[DelJo63]

Pan Wah is correct. The router has the technology to perform NAT (Network Address Translation).
The WAN side connection will have the public IP assigned by the ISP and all the LAN ports on the router will have the
internal (ie: non-routable, private) addresses. In this case, the non-routable refer to the fact that 100million users have Class C
addresses like 192.168.x.x so clearly they can't be routed beyond the subnet gateway (ie our personal routers).