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5.5 Auto-Negotiation
The STP ports on the Switch have built-in "Auto-negotiation". This technology automatically sets the best possible bandwidth
when a connection is established with another network device (usually at Power On or Reset). This is done by detect the modes
and speeds at the second of both device is connected and capable of, both 10BASE-T and 100BASE-TX devices can connect
with the port in either Half- or Full-Duplex mode.
If attached device is:
10Mbps, no auto-negotiation
10Mbps, with auto-negotiation
100Mbps, no auto-negotiation
100Mbps, with auto-negotiation
6. Power over Ethernet Overview
What is PoE?
The PoE is an abbreviation of Power over Ethernet; the PoE technology means a system to pass electrical power safely, along
with data on Ethernet UTP cable. The IEEE standard for PoE technology requires Category 5 cable or higher for high power
PoE levels, but can operate with category 3 cable for low power levels. Power is supplied in common mode over two or more of
the differential pairs of wires found in the Ethernet cables and comes from a power supply within a PoE-enabled networking
device such as an Ethernet switch or can be injected into a cable run with a mid-span power supply.
The original IEEE 802.3af-2003 PoE standard provides up to 15.4 W of DC power (minimum 44 V DC and 350mA) to each
device. Only 12.95 W is assured to be available at the powered device as some power is dissipated in the cable. The updated
IEEE 802.3at-2009 PoE standard also known as PoE+ or PoE plus, provides up to 25.5 W of power. The 2009 standard
prohibits a powered device from using all four pairs for power. The 802.3af / 802.3at define two types of source equipment:
Mid-Span and End-Span.
Mid-Span
Mid-Span device is placed between legacy switch and the powered device. Mid-Span is tap the unused wire pairs 4/5 and 7/8 to
carry power, the other four is for data transmit.
End-Span
End-Span device is direct connecting with power device. End-Span could also tap the wire 1/2 and 3/6.
PoE System Architecture
The specification of PoE typically requires two devices: the Powered Source Equipment (PSE) and the Powered Device (PD).
The PSE is either an End-Span or a Mid-Span, while the PD is a PoE-enabled terminal, such as IP Phones, Wireless LAN, etc.
Power can be delivered over data pairs or spare pairs of standard CAT-5 cabling.
100BASE-TX port will set to:
10Mbps.
10/20Mbps (10BASE-T/Full-Duplex)
100Mbps
100/200Mbps (100BASE-TX/Full-Duplex)
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