Cisco Systems 78-11741-02 manual Mobile IP Security, IPC-163

Configuring Mobile IP

How Mobile IP Works

Figure 28 Mobile IP Typical Packet Forwarding
Mobile node		Mobile node
visiting foreign
network		at home
	Internet

Foreign			Home
network	Foreign	Home	network
	agent	agent

Correspondent

node

53031

Mobile IP Security

Mobile IP provides the following guidelines on security between its components:

•Communication between MN and HA must be authenticated.

•Communication between MN and FA can optionally be authenticated.

•Communication between FA and HA can optionally be authenticated.

Also, communication between an active HA and a standby HA, as implemented when using the HA redundancy feature, must be authenticated. For more information on this feature, see the “Home Agent Redundancy” section later in this chapter.

MN-HA

In particular, the Mobile IP registration process is vulnerable to security attacks, because it informs the HA where to tunnel packets to a traveling MN. An illegitimate node could send a bogus registration request to an HA and cause all packets to be tunneled to the illegitimate node instead of the MN. This type of attack, called a denial-of-service attack, prevents the MN from receiving and sending any packets. To prevent denial-of-service attacks, Mobile IP requires that all registration messages between an MN and an HA be authenticated.

Cisco IOS software supports the Mobile-Home Authentication Extension (MHAE). All registration messages between an MN and an HA include a mandatory authentication extension.

Message Digest 5 (MD5) is an algorithm that takes the registration message and a key to compute the smaller chunk of data, called a message digest, plus a secret key. The MN and HA both have a copy of the key, called a symmetric key, and authenticate each other by comparing the results of the computation.

The time stamp is an identifier in the message that ensures the origination of the registration request and the time it was sent, thereby preventing replay attacks. A replay attack occurs when an individual records an authentic message that was previously transmitted and replays it at a later time. The time stamp is also protected by MD5.

Cisco IOS IP Configuration Guide

IPC-163