Connecting Interfaces - Cisco 3750G - Catalyst Integrated Wireless LAN Controller Configuration Manual

Chapter 11 Configuring Interface Characteristics
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For information on configuring a PoE port, see the
Port" section on page

Connecting Interfaces

Devices within a single VLAN can communicate directly through any switch. Ports in different VLANs
cannot exchange data without going through a routing device. With a standard Layer 2 switch, ports in
different VLANs have to exchange information through a router.
By using the switch with routing enabled, when you configure both VLAN 20 and VLAN 30 with an
SVI to which an IP address is assigned, packets can be sent from Host A to Host B directly through the
switch with no need for an external router
Figure 11-1
172.20.128.1
OL-8550-02
You can specify the maximum wattage that is allowed on the port. If the IEEE class maximum
wattage of the powered device is greater than the configured maximum value, the switch does not
provide power to the port. If the switch powers a powered device, but the powered device later
requests through CDP messages more than the configured maximum value, the switch removes
power to the port. The power that was allocated to the powered device is reclaimed into the global
power budget. If you do not specify a wattage, the switch delivers the maximum value. Use the auto
setting on any PoE port. The auto mode is the default setting.
static—The switch pre-allocates power to the port (even when no powered device is connected) and
guarantees that power will be available for the port. The switch allocates the port configured
maximum wattage, and the amount is never adjusted through the IEEE class or by CDP messages
from the powered device. Because power is pre-allocated, any powered device that uses less than or
equal to the maximum wattage is guaranteed to be powered when it is connected to the static port.
The port no longer participates in the first-come, first-served model.
However, if the powered-device IEEE class is greater than the maximum wattage, the switch does
not supply power to it. If the switch learns through CDP messages that the powered device needs
more than the maximum wattage, the powered device is shutdown.
If you do not specify a wattage, the switch pre-allocates the maximum value. The switch powers the
port only if it discovers a powered device. Use the static setting on a high-priority interface.
never—The switch disables powered-device detection and never powers the PoE port even if an
unpowered device is connected. Use this mode only when you want to make sure power is never
applied to a PoE-capable port, making the port a data-only port.
11-21.
Connecting VLANs with the Catalyst 3750 Switch
SVI 1
Host A
VLAN 20
"Configuring a Power Management Mode on a PoE
(Figure 11-1).
Layer 3 switch
with routing enabled
VLAN 30
Catalyst 3750 Switch Software Configuration Guide
Understanding Interface Types
SVI 2 172.20.129.1
Host B
11-9