VLAN, QoS, and Proxy Mobile IP
Proxy mobile IP

Layer 2 Roaming/IAPP
Network designers working with mobile users in a large area will often find it necessary to deploy more than one access point. The 802.11 standard does not define how access points track moving users or how to negotiate a handoff from one access point to the next, a process referred to as roaming. Several companies have introduced proprietary Inter-Access Point Protocols (IAPP) to support roaming. IAPP accomplishes roaming within a subnet. However, it does not address how the wireless system tracks users moving from one subnet to another when the same session must be maintained, as in the case of voice calls .

Layer 3 Roaming/Mobile IP
Where wireless is being deployed across multiple subnets, there are options to achieve seamless roaming. Wireless client adapters can contain proprietary client IP stacks that understand mobility and allow roaming between subnets. All mobile users on the network must have this software installed .

Layer 3 Roaming/Proxy Mobile IP
Another option is to have the wireless infrastructure contain the intelligence to perform the task. Cisco’s Proxy Mobile IP delivers this functionality. Mobile IP is designed for use in even the most complex network environments. As the wireless station leaves one area and enters the next, the new access point queries the station for its home agent. After it has been located, packet forwarding is established automatically between the new and old access points to ensure the user can transparently exchange data.

Standard Mobile IP
Standard Mobile IP requires IT personnel to install Mobile IP client software on all clients.

Proxy Mobile IP
Proxy Mobile IP does not require IT personnel to install client software on every client. However it does require firmware to be installed and configured on the routers to support the Home Agent/Forwarding Agent function. The access points will also need to be configured to support Proxy Mobile IP, as shown in Figures , , and .