Wireless/Redundant Edge Services xl Module Management and Configuration Guide WS.02.xx and greater

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Introduction
ProCurve Wireless Edge Services xl Module
Reserving VLANs for Wireless Users in a Network with
Multiple Wireless Edge Services xl Modules
A network that has more than one Wireless Edge Services xl Module intro-
duces another factor that you must consider: roaming between the modules.
To facilitate roaming and consistent network services, every module should
assign the same WLAN to the same VLAN (subnetwork) when possible.
Note The instructions in the rest of this section are based on the assumption that
the same VLAN ID corresponds to the same subnetwork throughout your
network. This assumption is usually, but not always, true. The important
consideration for roaming is that modules assign traffic in the same WLAN to
the same subnetwork.
Sometimes, however, your network design makes it impossible for modules
to forward traffic on the same subnetworks. If so, using the same VLAN ID for
the WLAN on every module is no longer valid. Instead configure Layer 3
roaming, making sure to associate each different subnetwork with a different
VLAN ID. See “Roaming Between RPs on Different Wireless Edge Services xl
Modules at Layer 3” on page 1-83.
If the VLAN and subnetwork that you choose for the WLAN is one used in the
traditional wired network, the design is much the same as that for a network
with a single module. If you want to reserve the VLAN for wireless users,
however, you must alter the design slightly. You must be careful not to
terminate the VLAN for wireless users on each module. Instead, extend the
VLAN through your infrastructure. However, do not configure the infrastruc-
ture devices to route traffic in and out of this VLAN but simply to forward the
VLAN traffic between the modules.
This design addresses several issues. When a station first associates to an RP,
the module that supports that RP assigns the station a DHCP address with
itself as the default gateway. If the station later roams to a new module, its
traffic must be able to reach the original module. In addition, when all modules
use the same Layer 2 subnetwork, they can exchange pre-authentication
messages, speeding roaming in WLANs that require 802.1X authentication.
Figure 1-9 shows a network that includes multiple Wireless Edge Services xl
Modules and separates VLANs for the wireless network from VLANs for the
wired network.