Layer-3 roaming

Allowing payload data from the wireless LAN to pass-through the WLC tunnel to the controller enables roaming even beyond the limits of broadcast domains. In this example application, a layer-3 switch between the floors prevents the transmission of broadcasts, and thus separates the broadcast domains.

In this example, two user groups A and B each have access to their own WLAN (SSID). On all floors of the building, the access points provide two SSIDs, 'GROUP_A' and 'GROUP_B'.

The diagram shows a sample application with the following components:

• The network consists of three segments on separate floors of a building.
• A central layer-3 switch connects the segments and divides the network into three broadcast domains.
• Each segment uses its own IP address space and its own VLAN.
• Each segment operates a local DHCP server, which transmits the following information to the access points:
  • IP address of the gateway
  • IP address of the DNS server
  • Domain suffix
    Note: This information enables the access points to contact the WLC controller in another broadcast domain.

The aim of the configuration: When moving to another floor, a WLAN client that associates with a particular SSID is to retain access to its "own" WLAN, regardless of which access point is being used and regardless of the segment in which the client is located. Since the segments in this example use different IP address ranges, this scenario can only be implemented by managing the access points directly with the central WLAN controller via layer 3 and across the boundaries of the VLANs.