Cisco Systems 78-11741-02 Wireless Office Headset User Manual


 
Configuring Mobile IP
How Mobile IP Works
IPC-161
Cisco IOS IP Configuration Guide
Figure 27 Mobile IP Components and Relationships
An MN is a node, for example, a PDA, a laptop computer, or a data-ready cellular phone, that can change
its point of attachment from one network or subnet to another. This node can maintain ongoing
communications while using only its home IP address.
An HA is a router on the home network of the MN that maintains an association between the home IP
address of the MN and its care-of address, which is the current location of the MN on a foreign or visited
network. The HA redirects packets by tunneling them to the MN while it is away from home.
An FA is a router on a foreign network that assists the MN in informing its HA of its current care-of
address. The FA detunnels and delivers packets to the MN that were tunneled by the HA. The FA also
acts as the default router for packets generated by the MN while it is connected to the foreign network.
It is recommended that HA and FA functionality be designed with interfaces with line protocol states
that are normally up.
How Mobile IP Works
This section explains how Mobile IP works. The Mobile IP process includes three main phases, which
are discussed in the following sections:
Agent Discovery
Registration
Routing
Agent Discovery
During the agent discovery phase, HAs and FAs advertise their presence on their attached links by
periodically multicasting or broadcasting messages called agent advertisements. MNs listen to these
advertisements and determine if they are connected to their home link or a foreign link. Rather than
waiting for agent advertisements, an MN can also send an agent solicitation. This solicitation forces any
agents on the link to immediately send an agent advertisement.
Mobile node
visiting foreign
network
Mobile node
at home
Internet
Foreign
network
Home
network
Foreign
agent
Home
agent
Foreign
network
Foreign
agent
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