Dell PowerConnect W-IAP92 Dell Instant 6.1.3.4-3.1.0.0 User Guide - Page 93

Chapter 6 Layer-3 Mobility IAPs form a single Instant network when they are in the same L2 domain. As the number of clients increase, multiple subnets are required to avoid broadcast overhead. In such a scenario, a client should be allowed to roam away from the Instant network to which it first connected (home network) to another Instant network supporting the same WLAN access parameters (foreign network) and continue its existing sessions. Layer-3 mobility allows a client to roam without losing its IP address and sessions. If WLAN access parameters are same across these networks, clients connected to APs in a given Instant network can roam to APs in a foreign Instant network and continue their existing sessions. Clients roaming across these networks are able to continue using their IP addresses after roaming. You can configure a list of Virtual Controller IP addresses across which L3 mobility is supported. Overview Dell Instant layer-3 mobility solution defines a Mobility Domain as a set of Instant networks, with same WLAN access parameters, across which client roaming is supported. The Instant network to which the client first connects is called its home network. When the client roams to a foreign network, an AP in the home network (home AP) anchors all traffic to or from this client. The AP to which the client is connected in the foreign network (foreign AP) tunnels all client traffic to or from the home AP through a GRE tunnel. Figure 83 Shows the routing of traffic when the client is away from its home network When a client first connects to an Instant network, a message is sent to all configured Virtual Controller IP addresses to see if this is an L3 roamed client. On receiving an acknowledgement from any of the configured Virtual Controller IP addresses, the client is identified as an L3 roamed client. If the AP has no GRE tunnel to this home network, a new tunnel is formed to an AP (home AP) from the client's home network. Each foreign AP has only one home AP per Instant network to avoid duplication of broadcast traffic. Separate GRE tunnels are created for each foreign AP / home AP pair. If a peer AP is a foreign AP for one client and a home AP for another, two separate GRE tunnels are used to handle L3 roaming traffic between these APs. Dell PowerConnect W-Series Instant Access Point 6.1.3.4-3.1.0.0 | User Guide Layer-3 Mobility | 93