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Overview of the SCALANCE WLC711 Solution

SCALANCE WLC711 and Your Network

SCALANCE WLC711

User Guide, V8.11, 07/2012, C79000-G8976-C260-03 1-13

Routing

Routing can be used on the SCALANCE IWLAN Controller to support the VNS definitions.

Through the user interface you can configure routing on the SCALANCE IWLAN Controller to

use one of the following routing techniques:

• Static routes — Use static routes to set the default route of a SCALANCE IWLAN Controller

so that legitimate wireless device traffic can be forwarded to the default gateway.

• Open Shortest Path First (OSPF, version 2) (RFC2328) — Use OSPF to allow the SCALANCE

IWLAN Controller to participate in dynamic route selection. OSPF is a protocol designed for

medium and large IP networks with the ability to segment routes into different areas by

routing information summarization and propagation. Static Route definition and OSPF

dynamic learning can be combined, and the precedence of a static route definition over

dynamic rules can be configured by selecting or clearing the Override dynamic routes option

checkbox.

• Next-hop routing — Use next-hop routing to specify a unique gateway to which traffic on a

VNS is forwarded. Defining a next-hop for a VNS forces all the traffic in the VNS to be

forwarded to the indicated network device, bypassing any routing definitions of the

controller's route table.

Mobility and Roaming

In typical simple configurations, APs are set up as bridges that bridge wireless traffic to the local

subnet. In bridging configurations, the user obtains an IP address from the same subnet as the AP,

assuming no VLAN trunking functionality. If the user roams between APs on the same subnet, it

is able to keep using the same IP address. However, if the user roams to another AP outside of that

subnet, its IP address is no longer valid. The user's client device must recognize that the IP address

it has is no longer valid and re-negotiate a new one on the new subnet. This mechanism does not

mandate any action on the user. The recovery procedure is entirely client device dependent. Some

clients automatically attempt to obtain a new address on roam (which affects roaming latency),

while others will hold on to their IP address. This loss of IP address continuity seriously affects the

client's experience in the network, because in some cases it can take minutes for a new address to

be negotiated.

The SCALANCE WLC711 solution centralizes the user's network point of presence, therefore

abstracting and decoupling the user's IP address assignment from that of the APs location subnet.

That means that the user is able to roam across any AP without losing its own IP address,

regardless of the subnet on which the serving APs are deployed.

In addition, a SCALANCE IWLAN Controller can learn about other SCALANCE IWLAN

Controllers on the network and then exchange client session information. This enables a wireless

device user to roam seamlessly between different Wireless APs on different SCALANCE IWLAN

Controllers.

Network Availability

The SCALANCE WLC711 solution provides availability against Wireless AP outages, controller

outages, and even network outages. The SCALANCE IWLAN Controller in a VLAN bridged

topology can potentially allow the user to retain the IP address in a failover scenario, if the VNS/

VLAN is common to both controllers. For example, availability is provided by defining a paired

controller configuration by which each peer can act as the backup controller for the other's APs.

APs in one controller are allowed to fail over and register with the alternate controller.

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