Cisco Systems DL-2159-05 manual Mobile IP Environment

Chapter 6 Configuring Proxy Mobile IP

Introduction to Mobility in IP

Figure 6-2

MN

The Mobile IP Environment

				CN, Correspondent Node
				Destination IP host in session with
				a Mobile Node
HA		CN
	Internet
				FA, Foreign Agent
			FA	Provides an addressable point of
				attachment to the MN Care Of
HA, Home Agent	COA			Address (COA)
				Maintains an awareness for all
Maintains an association between
				visiting MNs
the MN's "home" IP address and its
				Acts as a "relay" between the MN
care of address (loaned address) on
the foreign network				and its Home Agent
Redirects and tunnels packets to the				Receives all packets for the MN
care of address on the foreign				from the MN's Home Agent
network
	MN
	MN, Mobile Node
	An IP host that maintains network
	connectivity using its "home" IP address,				90541
	regardless of which subnet (or network) it

is connected to

In order for a mobile node (MN) to successfully roam across subnets it must first be anchored to its home network. The home agent (HA) is the router that serves as that anchor. The home agent contains a list of all devices (by IP address) that are capable of roaming from its network. After the mobile node roams to a new network, it must register with the home agent as being away from home. Its registration is sent by way of the Foreign Agent (FA), the router providing service on the foreign network. The foreign agent includes a care-of address in the registration it sends to the home agent. This address is used as the termination address of the tunnel on the foreign router. A tunnel is then built between the home agent and the foreign agent for all traffic destined for the mobile node.

When a mobile node sends traffic to another device (known as a correspondence node or correspondence host), such as a web server, the outbound traffic is routed directly to the destination device. The destination device replies to the source IP address, resulting in the the traffic being routed to the home agent because it is the default router for the subnet from which the mobile node originated. The home agent then forwards the traffic through the tunnel to the foreign agent, which forwards it to the mobile node. Figure 6-3provides an example of this process.

Cisco Aironet 1200 Series Access Point Software Configuration Guide

6-4 OL-2159-05