Cisco Aironet Access Points

Proxy Mobile IP implementation on Cisco Aironet products is intended to provide Mobile IP functionality on behalf of the roaming mobile devices. It supports mobility in the IP infrastructure, allowing users to keep the same IP address and maintain ongoing applications while roaming between IP networks. The roaming individual could continue communication without sessions or connections being dropped. This proxy Mobile IP functionality is provided without the need for any Mobile IP-capable software running on the devices.

Proxy Mobile IP has four main phases.

Agent discovery - The access point discovers the foreign and home agents.
Subnet map exchange - The access point obtains information regarding other mobile device's home agents during the subnet map exchange.
Registration - The access point registers the mobile devices with the foreign agent and home agent during registration.
Tunneling - A reciprocal tunnel is set up by the home agent to the current location of the mobile device on the foreign network. Packets are routed to the mobile device as it roams.
Proxy Mobile IP

This feature can be enabled only if your device is not in repeater mode. Enable proxy Mobile IP on at least one SSID. Proxy mobile IP must be enabled for each SSID supporting it (see the SSID page). To fully enable Proxy mobile IP, either Current SA Bindings List must be created (see Proxy Mobile IP Advanced page) or Proxy Mobile IP Server must be set (see Server Manager page). If you disable proxy Mobile IP, your entire proxy Mobile IP configuration is cleared, including your security parameter index (SPI) and key entries (see Proxy Mobile IP Advanced page).

Authoritative Access Points (host name or IP Address)

An authoritative access point (AAP) must be specified in order to use the proxy Mobile IP feature. These AAPs keep track of the home agent information on all of the mobile devices. They keep the latest subnet map table, which maps client IP addresses to home agent addresses. This information is needed to activate the proxy Mobile IP functionality.

An access point sends packets with the subnet and home agent information to the AAP. The AAP distributes this information (in the form of a table) to all the access points participating in the PMIP network. By having this information local, the access point can do a faster lookup for the home agent information when a foreign mobile device roams into the network. If an access point is unreachable during this update process, the AAP retries. If the retry fails, the next configured AAP is tried. You should have more than one AAP in the system so that you do not lose subnet map table information if an AAP goes down. To rebuild the subnet table, you must either reboot all your access points or clear the subnet map table from each one.