LANCOM WLC series
Chapter 1: Centralized WLAN management
13
EN
1.2.3
Communication between the Access Point and the WLAN
Controller
As of firmware version LCOS 7.20 there is a difference between
LANCOM Access Points (such as the LANCOM L-54ag) and LANCOM
Wireless Routers (such as the LANCOM 1811n Wireless) with regard
to the ex-factory standard settings in the WLAN modules. In the fol-
lowing specifications, the general term Access Point will be used for
the most part.
Fôr a sucessful starting up the Access Points must comply with the following
requirements:
The Access Point has an IP address (static or assigned via DHCP)
The Access Point can reach a WLAN Controller in the LAN via broadcast
Alternatively: The Access Point can resolve the address on a WLAN
Controllers in the WAN using a DNS server (the “WLC-Address” is resolved
using “.company.intern”).
For a WLAN Controller in the WAN the firewall allows the communication
for DNS, CAPWAP at UDP Port 1027 and HTTP for SCEP.
Communication between an Access Point and the WLAN Controller is always
initiated by the Access Point. In the following cases, the devices search for a
WLAN Controller that can assign a configuration to them:
A LANCOM Access Point has the factory settings and is not yet configured.
In these settings the WLAN modules are deactivated; the Access Point
searches for a WLAN Controller in the LAN.
CAPWAP tunneling and layer- 3 roaming
From one of the later LCOS versions, LANCOM WLAN Controllers also support transfer of the
payload data through a CAPWAP tunnel.
This allows selected applications such as VoIP to be routed via the central WLAN Controller,
for example. If WLAN clients change to a different radio cell, the underlying IP connection
will not be interrupted because it continues to be managed by the central WLAN Controller
(layer-3 roaming). In this way, mobile SIP telephones can easily roam even during a call—
between Ethernet subnets.
Managing data streams centrally can also make configuring VLANs at the switch ports
unnecessary in environments with numerous VLANs because all CAPWAP tunnels are cen-
trally managed on the WLAN Controller.
