Concept Guide

330 | Mobility and Client Management Dell Networking W-Series Instant 6.4.3.1-4.2.0.0 | User Guide
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.
If client subnet discovery fails on association due to some reason, the foreign AP identifies its subnet when it
sends out the first L3 packet. If the subnet is not a local subnet and belongs to another Instant network, the
client is treated as an L3 roamed client and all its traffic is forwarded to the home network through a GRE
tunnel.
Configuring L3-Mobility
To configure a mobility domain, you have to specify the list of all Instant networks that form the mobility
domain. To allow clients to roam seamlessly among all the APs, specify the Virtual Controller IP for each foreign
subnet. You may include the local Instant or Virtual Controller IP address, so that the same configuration can
be used across all Instant networks in the mobility domain.
It is recommended that you configure all client subnets in the mobility domain. When client subnets are
configured:
l If a client is from a local subnet, it is identified as a local client. When a local client starts using the IP address,
the L3 roaming is terminated.
l If the client is from a foreign subnet, it is identified as a foreign client. When a foreign client starts using the
IP address, the L3 roaming is set up.
Home Agent Load Balancing
Home Agent Load Balancing is required in large networks where multiple tunnels might terminate on a single
border or lobby AP and overload it. When load balancing is enabled, the Virtual Controller assigns the home AP
for roamed clients by using a round robin policy. With this policy, the load for the APs acting as Home Agents
for roamed clients is uniformly distributed across the W-IAP cluster.
Configuring a Mobility Domain for Instant
You can configure L3 mobility domain by using the Instant UI or CLI.
In the Instant UI
To configure a mobility domain, perform the following steps:
1. Click the System link at top right corner of the Instant main window. The System window is displayed.
2. Click the Show advanced options link. The advanced options are displayed.
3. Click L3 Mobility. The L3 Mobility window is displayed.