WESM zl Management and Configuration Guide WT.01.XX and greater

9-23
Fast Layer 2 Roaming and Layer 3 Mobility
Verifying and Managing Layer 3 Mobility
The Idle status indicates that the local Wireless Edge Services zl 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 zl 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 zl Module and the peer cannot reach
each other.
Make sure that each module can ping all other members of the Layer 3
mobility domain. The local IP addresses must be on VLANs that are tagged
on the uplink VLAN. And either the modules themselves or the modules’
default gateways must 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 zl 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 zl
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.