user manual

6-8
Cisco Aironet 1200 Series Access Point Software Configuration Guide
OL-2159-05
Chapter 6 Configuring Proxy Mobile IP
Introduction to Mobility in IP
• A home agent. The home agent is a router on the visiting client’s home network that serves as the
anchor point for communication with the access point and the visiting client. The home agent
tunnels packets from a correspondent node on the Internet to the visiting client device by way of a
tunnel to a foreign agent.
• A foreign agent. The foreign agent is a router on your network that serves as the point of attachment
for the visiting client device when it is on your network, delivering packets from the home agent to
the visiting client.
Figure 6-4 shows the five participating devices.
Figure 6-4 Participating Devices in Proxy Mobile IP
How Proxy Mobile IP Works
The proxy Mobile IP process has four main phases. These sections describe each phase:
• Agent Discovery, page 6-8
• Subnet Map Exchange, page 6-9
• Registration, page 6-10
• Tunneling, page 6-10
Agent Discovery
During the agent discovery phase, the home agent and the foreign agent advertise their services on the
network by using the IRDP. The access point monitors these advertisements.
The IRDP advertisements carry mobile IP extensions that specify whether an agent is a home agent,
foreign agent, or both; its care-of address; the types of services it provides, such as reverse tunneling and
generic routing encapsulation (GRE); and the allowed registration lifetime or roaming period for visiting
Internet
Foreign
agent
Access point
supporting proxy
Mobile IP
Home
agent
Access point
supporting proxy
Mobile IP
Client device
at home
Client device
visiting foreign
network
Authoritative
access point
supporting proxy
Mobile IP
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