foreign network
In the Mobile Internet Protocol (Mobile IP), a foreign network is any network other than the home network to which a mobile device may be connected.
Because standard Internet routing mechanisms deliver all traffic to a device's home network, it was once necessary to change a mobile device's IP address each time it connected through a foreign network. To overcome this drawback, the Internet Engineering Task Force (IETF) has developed the Mobile IP standard and several enhancements to it.