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

Table Of Contents
9-9
Fast Layer 2 Roaming and Layer 3 Mobility
Overview
Seamless roaming—The defining feature of a seamless roam is not
speed, but preservation of the users authentication, IP address, and active
sessions. The user does not need to re-login, and a user browsing the
Internet probably would not notice a seamless roam; a user accessing a
real-time application may detect a slight lag.
Not seamless roaming—If a roam is not seamless, the user must log in
again so that his or her station can re-authenticate or change its IP address.
A Wireless Edge Services xl Module handles roaming between its own RPs
automatically—this roaming is always fast. To enable the best possible roam-
ing between RPs adopted by different modules, however, you may need to
take some additional steps.
If you configure and group your modules correctly, you can always enable at
least seamless, and sometimes fast, roaming. Table 9-1 explains how to enable
the best possible roaming depending on the WLAN’s security and on whether
the roam occurs at Layer 2 or Layer 3.
Table 9-1. Enabling the Best Roaming Between Different Wireless Edge Services
xl Modules
WLAN Security
Option
Layer 2 Roam
Without Special
Configuration
Best
Layer 2
Roam
Requirements for
Best Layer 2
Roam
Layer 3 Roam
Without Special
Configuration
Best
Layer 3
Roam
Requirements for
Best Layer 3
Roam
open
authentication
seamless seamless none not seamless seamless modules in the
same Layer 3
mobility domain
authentication
with a static key
(static Wired
Equivalent Privacy
[WEP] or WPA-
preshared key
[PSK])
seamless seamless none not seamless seamless modules in the
same Layer 3
mobility domain
Web-Auth not seamless seamless 48 RP limit, either:
•a single
module adopts
all RPs
modules in the
same
redundancy
group
not seamless seamless modules in the
same Layer 3
mobility
domain
dynamic WEP or
RADIUS MAC
authentication
seamless seamless none not seamless seamless modules in the
same Layer 3
mobility domain