user manual

6-5
Cisco Aironet 1200 Series Access Point Software Configuration Guide
OL-2159-05
Chapter 6 Configuring Proxy Mobile IP
Introduction to Mobility in IP
Figure 6-3 The Mobile IP Traffic Pattern
When the mobile node roams back to its home network, it drops its registration with the home agent and
the tunnel is removed. If more than one node has roamed from the same home network to the same
foreign network, a single tunnel is used to service traffic for all mobile devices between those two tunnel
end points.
The protocol used to exchange information between the home agent and mobile node is the Internet
Control Message Protocol (ICMP) Router Discovery Protocol (IRDP). Extensions have been added to
this protocol to accommodate Mobile IP operation. Mobile IP features on a Cisco router require the IP
Plus Feature Set or better.
Proxy Mobile IP Explained
The Mobile IP operation detailed above relies upon the mobile node using specialized Mobile IP client
software. This software provides the intelligence needed to communicate with other Mobile IP entities
such as home and foreign agents, plus the ability to generate registrations as appropriate. However, there
are a few aspects of this method that make it undesirable. They include the cost of client software, the
amount of administration required to load it onto some (potentially large) number of devices, and the
possibility that the population of mobile nodes may not be immediately known or may change over time.
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Correspondent
Host
Foreign
Agent
Home
Agent
MN
Mobile
Node
Internet
- Traffic is sent from the MN directly to the Correspondent Host
- The Host replies to the source address of theMN
- The traffic is routed to the HA
- The HA tunnels the traffic to the CoA of the FA
- The FA forwards the traffic to the MN