Specifications

Chapter 6 Configuring Proxy Mobile IP
Proxy Mobile IP
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Cisco Aironet Access Point Software Configuration Guide
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the agent discovery mechanism. It sends this information to another access point
called an authoritative access point (AAP). The AAP is an access point that
maintains the latest subnet map table.
When the AAP receives the new information, it replies to the access point with a
copy of the latest subnet map table. The new access point now has the latest subnet
map table locally and it is ready to perform proxy Mobile IP for visiting clients.
Having the subnet map table locally helps the access point do a quick lookup for
the home agent information. Meanwhile, the AAP adds the new access point to its
list of access points and the home agent information to its subnet map table. The
AAP then updates all the other access points with this additional piece of
information.
You can designate up to three AAPs on your wireless LAN. If an access point fails
to reach the first AAP, it tries the next configured AAP. The AAPs compare their
subnet map tables periodically to make sure they have the same subnet map table.
If the AAP detects that there are no more access points for a particular home
agent, it sends an invalid registration packetwith a bad SPI and group key using
the broadcast address of the home agent subnet to determine if the home agent is
still active. If the home agent responds, the AAP keeps the home agent entry in
the subnet map table even though there are no access points in the home agent's
subnet. This process supports client devices that have already roamed to foreign
networks. If the home agent does not respond, the AAP deletes the home agent
entry from the subnet map table.
When a client device associates to an access point and the access point determines
that the client is visiting from another network, the access point performs a
longest-match lookup on its subnet map table and obtains the home agent address
for the visiting client. When the access point has the home agent address, it can
proceed to the registration step.
Registration
The access point is configured with the mobility security association (which
includes the shared key) of all potential visiting clients with their corresponding
home agents. You can enter the mobility security association information locally
on the access point or on a RADIUS server on your network, and access points
with proxy Mobile IP enabled can access it there.
The access point uses the security association information, the visiting client’s IP
address, and the information that it learns from the foreign agent advertisements
to form a Mobile IP registration request on behalf of the visiting client. It sends