This paper describes a concept combining mobile IP and ad hoc routing to create a robust mobile network. In this network all nodes are mobile and globally and locally reachable under the same IP address. Essential for implementing this network are the dynamic mobile IP routers. They act as gateways to the rest of the Internet for mobile nodes in the mobile network and as entry point to the mobile network for hosts in the Internet requesting services from the mobile nodes in the mobile network. The routers are connected to two different wireless networks. On the ingress side they connect to a mobile ad hoc network while on the egress side they connect to a cellular network offering access to the rest of the Internet. The network is robust in the sense that nodes can use different gateways and the network can split up into several parts while maintaining reachability between the nodes in the different parts and the Internet as long as every part contains at least one gateway. These parts can later join and form one ad hoc network again where the nodes can reach each other without using gateways. The concept is based on the Mobile IPv4 protocol and its working was demonstrated using Mobile IPv4 implementation and AODV over WLAN and GPRS within the SPEARS project. © 2004 IEEE.