3-5
Cisco Wireless LAN Controller Configuration Guide
OL-17037-01
Chapter 3 Configuring Ports and Interfaces
Overview of Ports and Interfaces
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The Catalyst 3750G Integrated Wireless LAN Controller Switch has two internal Gigabit Ethernet
distribution system ports (ports 27 and 28) that connect the switch and the integrated controller.
These internal ports are located on the switch backplane and are not visible on the front panel. Each
port is capable of managing up to 48 access points. However, Cisco recommends no more than 25
access points per port due to bandwidth constraints. The -S25 and -S50 models allow a total of 25
or 50 access points to join the controller.
Note
Refer to the
“Configuring a 4400 Series Controller to Support More Than 48 Access Points” section on
if you want to configure your Cisco 4400 series controller to support more than 48 access
points.
Each distribution system port is, by default, an 802.1Q VLAN trunk port. The VLAN trunking
characteristics of the port are not configurable.
Note
Some controllers support link aggregation (LAG), which bundles all of the controller’s distribution
system ports into a single 802.3ad port channel. Cisco 4400 series controllers support LAG in software
release 3.2 and higher, and LAG is enabled automatically on the Cisco WiSM controllers. Refer to the
“Enabling Link Aggregation” section on page 3-29
for more information.
Service Port
Cisco 4400 series controllers also have a 10/100 copper Ethernet service port. The service port is
controlled by the service-port interface and is reserved for out-of-band management of the controller and
system recovery and maintenance in the event of a network failure. It is also the only port that is active
when the controller is in boot mode. The service port is not capable of carrying 802.1Q tags, so it must
be connected to an access port on the neighbor switch. Use of the service port is optional.
Note
The Cisco WiSM’s controllers use the service port for internal protocol communication between the
controllers and the Supervisor 720.
Note
The Cisco 2100 series controllers and the controller in the Cisco Integrated Services Router do not have
a service port.
Note
The service port is not auto-sensing. You must use the correct straight-through or crossover Ethernet
cable to communicate with the service port.
