Availability and Mobility
8.2 Mobility and the VN Manager
The Controller, Access Points and Convergence Software system has a technique by which multiple HiPath Wireless Controllers on a network can discover each other and exchange information about a client session. This enables a wireless device user to roam seamlessly between different Wireless APs on different HiPath Wireless Controllers.
The solution introduces the concept of a "VN Manager". This means that one HiPath Wireless Controller on the network must be designated as the "VN Manager". All other HiPath Wireless Controllers are designated as "VN Agents". To define whether the HiPath Wireless Controller is a Manager or an Agent, use the VN Manager screen in the HiPath Wireless Controller Configuration area.
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A Wireless AP connects first to a HiPath Wireless Controller registered as"ac_manager" and, if not found, then seeks an "ru_manager". If the primary HiPath Wireless Controller fails, the secondary one registers as "ru_manager". This enables the secondary HiPath Wireless Controller to be found by Wireless APs after they reboot.
Mobility and the VN Manager
The wireless device will keep the IP address, VNS assignment and filtering rules that it received from the HiPath Wireless Controller that it first connected to - its "home" HiPath Wireless Controller. (This information is collected in the Active Clients by VNS display on the home HiPath Wireless Controller.) The VNS on each HiPath Wireless Controller must have the same SSID. If the VNS has static WEP, it is recommended that the same key be used.
8.2.1 VN Manager and VN Agent: Background
The HiPath Wireless Controller that is the "VN Manager":● uses SLP to register itself (as “SiemensNet”) with the SLP Directory Agent
● listens for connection attempts from "VN Agents"
● if it receives a connection attempt from "VN Agent", establishes connection and sends a message to the "VN Agent" specifying the Heartbeat interval, and the VN Manager's IP address
● sends regular Heartbeat messages (which contain wireless device session changes and Agent changes) to the VN Agents and waits for an Update message back
● if it fails to receive an Update from the VN Agent after three Heartbeat messages, sends a Disconnect message to the VN Agent, removes all wireless device users associated with that VN Agent HiPath Wireless Controller from its tables and closes down the connection.
The HiPath Wireless Controller that is a "VN Agent":
● uses SLP to find the location of the VN Manager
● attempts to establish a TCP/IP connection with the VN Manager
● when it receives the connection-established message (see above), updates its tables, and sets up data tunnels to and between all HiPath Wireless Controllers it has been informed of
● after every Heartbeat massage received, uses the information to update its own tables and then sends an Update message to the VN Manager, with updates on wireless device users and data tunnels it is managing.
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The "VN Manager" concept relies on SLP and DHCP. Before you begin, you must ensure that the DHCP server on your network supports Option 78. These are also used during the Wireless AP discovery process, explained earlier in this Guide.Mobility and the VN Manager
Set up a HiPath Wireless Controller as a VN Manager
1. In the HiPath Wireless Controller Configuration screen, click on the VN Manager option.
The Virtual Network Settings for VN Manager screen appears.
2. From the Role drop-down list, select VN Manager (other options: None, Agent).
3. From the drop-down list, select the Port on the HiPath Wireless Controller to be used by the VN Manager process. Ensure that the port selected is routable on the network.
4. In the Heartbeat field, type in the time interval at which the VN Manager sends a Heartbeat message to a VN Agent. The default is 5 seconds.
5. To save these settings, click on the Save button.
If you set up one HiPath Wireless Controller on the network as a "VN Manager", then all other HiPath Wireless Controllers must be set up as "VN Agents". In the VN Manager screen, in the Role drop-down list, select Agent. The Heartbeat value for a "VN Agent" is how long to wait for a connection establishment response before trying again.
View additional displays when VN Manager is enabled
On a HiPath Wireless Controller has been configured as a VN Manager, three additional displays appear as options in the List of Displays screen:
● Client Location by Home: shows the active wireless clients, listed by their "Home" HiPath Wireless Controller
● Client Location by Foreign HWC: shows the active wireless clients, listed by the foreign HiPath Wireless Controller they are active on
Mobility and the VN Manager
● HWC Tunnel Traffic: shows the status of the tunnels between the HiPath Wireless Controllers.
To view the status of the tunnels between the HiPath Wireless Controllers, click on the HWC Tunnel Traffic option. This screen displays the HiPath Wireless Controllers known to the VN Manager. If a tunnel is active, a green band is displayed between HiPath Wireless Controllers.
A red band indicates that there is no traffic on the tunnel. If the HiPath Wireless Controllers are not displayed, the tunnel is inactive.
The Active Clients by VNS display also collects information on the VN Manager HiPath
Wireless Controllers of for all Wireless APs, and for the wireless devices that travel, if they are on the same SSID.
Management users