WESM zl Management and Configuration Guide WT.01.28 and greater

1-16
Introduction
ProCurve Wireless Edge Services zl Module
4. The module encapsulates the 802.11 frame. The encapsulation header includes
a tag for the Radio Port VLAN specified for the radio to which the destination
station has associated.
5. The module forwards the traffic toward its destination on its downlink port.
Layer 2 and Layer 3 Operation
You have been introduced to how the Wireless Edge Services zl Module receives,
processes, and forwards traffic. You can now become better acquainted with specific
operations that the module applies to traffic. For example, the module might apply
an ACL to the traffic or perform NAT on it. To understand when the module performs
specific functions, you must first understand how the module (and adopted RPs)
operate at Layer 2 and Layer 3.
The Wireless Edge Services zl Module’s downlink port and associated RPs function
as Layer 2 devices. The Wireless Edge Services zl Module itself, as well as its uplink
port, can operate at Layer 3 as well as Layer 2.
RP Operations
RPs typically function at Layer 2 and do not have IP addresses; the Wireless Edge
Services zl Module manages all communications with them.
In some configurations, however, an RP can receive an IP address and operate at
Layer 3. When an RP cannot reach a Wireless Edge Services zl Module at Layer 2,
it obtains a dynamic IP address and learns the module’s IP address. In this case, the
RP communicates with the module at Layer 3. See “Communications Between an
RP and the Wireless Edge Services zl Module: Layer 2 and Layer 3 Adoption” on
page 1-64.
Wireless Edge Services zl Module Operations
The downlink port does not have an IP address; it is tagged for the Radio Port VLAN,
and the module does not require an IP address on this VLAN.
The Wireless Edge Services zl Module operates at Layer 2 on its downlink port. On
the downlink port, the module receives encapsulated 802.11 frames. It decapsulates
and processes these frames and then bridges them to an Ethernet subnetwork
(VLAN). When transmitting traffic back to wireless stations, the module also acts at
Layer 2, forwarding traffic based on the associations to those stations.
After the module bridges a frame to a VLAN interface, the module can handle the
inner packet at Layer 3. Note that this VLAN interface may or may not be tagged on
the uplink port.