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

9-20
Fast Layer 2 Roaming and Layer 3 Mobility
Verifying and Managing Layer 3 Mobility
The Idle status usually indicates that the local Wireless Edge Services xl
Module has not enabled Layer 3 roaming. Even if the Enable Mobility box is
checked, the module does not enable Layer 3 mobility until you specify a valid
local IP address.
A Wireless Edge Services xl Module that remains at the Active-Connecting or
Passive-Connecting status also cannot connect to the peer. Usually, one of two
problems has occurred:
■ The local Wireless Edge Services xl Module and the peer cannot reach
each other.
Make sure that each module can ping all other members of the Layer 3
mobility domain. Either the modules themselves must know routes to
peers’ subnetworks, or the modules must have default gateways that
know the necessary routes.
■ The peer has not enabled Layer 3 mobility.
You should also check that this module and the peer enable mobility on the
same WLAN (or WLANs). Even when they do not, the peers can establish a
connection; however, but Layer 3 mobility will not function correctly on the
WLAN in question.
Tracking Peer Communications
Layer 3 mobility peers that have established a relationship exchange these
messages:
■ Join Events—A Wireless Edge Services xl Module sends a Join Event
when a station first associates with it. This message, which informs all
peers that the station has joined the Layer 3 mobility domain, contains the
station’s MAC address, IP address, and HM VLAN. The HM (the module
responsible for handling the station’s traffic) is typically the module that
sends the Join Event message.
■ Leave Events—A module informs its peers when a station disassociates
from the WLAN completely. (This is different from roaming to a new RP
or module.)
■ L2-Roams—A station performs a Layer 2 roam when it reassociates to a
new RP but its HM VLAN remains the same. Wireless Edge Services xl
Modules track only Layer 2 roams that occur between modules. Because
the new module supports the station’s HM VLAN, the new module does
not need to tunnel traffic back to the original HM. Instead, the new module
becomes the station’s new HM, sending out an L2-Roam message to notify
peers of the change.