Specifications

6-5
Cisco Aironet Access Point Software Configuration Guide
OL-0657-07
Chapter 6 Configuring Proxy Mobile IP
Proxy Mobile IP
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 client
devices. Rather than waiting for agent advertisements, an access point can send
out an agent solicitation. This solicitation forces any agents on the network to
immediately send an agent advertisement.
When an access point determines that a client device is connected to a foreign
network, it acquires a care-of address for the visiting client. The care-of address
is an IP address of a foreign agent that has an interface on the network being
visited by a client device. An access point can share this address among many
visiting client devices.
When the visiting client associates to an access point, the access point compares
the client’s IP address with that of its own IP network information and detects that
the client is a visitor from another network. The access point then begins the
registration. However, before the access point can begin the registration process
on behalf of the visiting client, it must have the home agent IP address of the
visiting client, which it gets from a subnet map table.
Subnet Map Exchange
Each access point with proxy Mobile IP enabled maintains a subnet map table.
The subnet map table consists of a list of home agent IP addresses and their subnet
masks. Ta bl e 6 -1 is an example of a subnet map table.
Access points use the subnet map table to determine the IP address of the visiting
client’s home agent. When an access point boots up or when proxy Mobile IP is
first enabled on an access point, it obtains its own home agent information using
Table 6-1 Example of a Subnet Map Table
Home Agent Subnet Mask
10.10.10.1 255.255.255.0
10.10.4.2 255.255.255.0
10.3.4.4 255.255.255.248
10.12.1.1 255.255.0.0