Mobile IP (Internet Protocol)

Mobile IP is an Internet Engineering Task Force (IETF) standard, outlined in RFC 2002. A number of other IETF standards also address Mobile IP, including RFC 2003, RFC 2004, RFC 2005, and RFC 2006.

This is an industry standard—not technology that's proprietary to Cisco. This means that, in theory, there should be interoperability between Mobile IP devices (no matter the brand), assuming they support the standard. Cisco Mobile IP is a suite of software that runs on different devices, including Mobile IP that runs on IOS routers and the Cisco Mobile Client for Windows.

One Mobile IP feature that you should be familiar with is Local-Area Mobility (LAM). This features allows a device to roam from a local IP subnet to another local IP subnet, all while keeping the same IP address. This means you could walk from network to network between buildings on a large campus while using your device.

To determine whether your router supports Mobile IP, go to the Global Configuration Mode prompt of your router, and enter the following:

ip mobile ?

Here's an example:

Router(config)#ip mobile ?
foreign-agent         Foreign Agent services
home-agent            Home Agent services
host                  Grouping of one or more mobile hosts
secure                Security association
tunnel                Mobile IP tunnel settings
virtual-network       IP address of virtual network
                     containing mobile hosts

Router(config)#ip mobile

You can accomplish most Mobile IP configuration using the ip mobile command. You also use this command to enable Mobile IP routing. Here's an example:

Router(config)# router mobile

Space constraints prevent me from discussing how to configure Mobile IP in this article. For more information on how Mobile IP works and to learn how to configure it, check out in Cisco's Mobile IP IOS Configuration Guide (need cisco name and password to access this resource). configuring Mobile IP and preventing users from experiencing any interruptions when roaming from LAN to WLAN to DSL to coffee shop can still be somewhat problematic.