TCP/IP Tutorial and Technical Overview - IBM Redbooks

When a mobile node moves from its home network and registers itself with a
foreign network, the home agent does a gratuitous ARP broadcast to update the
ARP caches of all local nodes in the network. The MAC address used is again
the MAC address of the home agent.
When a mobile node returns to its home network, having been previously
registered at a foreign network, gratuitous ARP is again used to update ARP
caches of all local nodes, this time with the real MAC address of the mobile node.
7.2.6 Mobile IP security considerations
The mobile computing environment has many potential vulnerabilities with
regard to security, particularly if wireless links are in use, which are particularly
exposed to eavesdropping. The tunnel between a home agent and the care-of
address of a mobile node can also be susceptible to interception unless a strong
authentication mechanism is implemented as part of the registration process.
RFC 3344 specifies implementation of keyed MD5 for the authentication protocol
and advocates the use of additional mechanisms (such as encryption) for
environments where total privacy is required.
7.3 RFCs relevant to this chapter
The following RFC provides detailed information about the connection protocols
and architectures presented throughout this chapter:
RFC 3344 – IP Mobility Support (August 2002)
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