Syngress - Eleventh Hour Network+ Exam N10-004 Study Guide (11 ...

Network Devices 41
balancing so that the amount of data transmitted across networks and requests
processed by a server is reduced.
EXAM WARNING
Switches may operate at more than one layer of the OSI model. They work at the data
link layer (Layer 2) and sometimes at the network layer (Layer 3) of the OSI model. Layer
3 switches have an integrated router function that allows them to make decisions as to
where the data should be sent.
ADVANCED FEATURES OF A SWITCH
Some switches offer enhanced features that bring improved security, services, and
capabilities that were unseen in basic switches that were available in previous
years. Some of the advanced features include the following:
Power over Ethernet (PoE) PoE is a technology in which electrical power
can be transferred over standard twisted-pair cables to provide power to
network devices. PoE allows data and electricity to also be transferred along
the same cabling.
Spanning Tree Protocol (STP) STP was developed to prevent broadcast
storms that result from looping. It uses an algorithm that identifies that a
switch has multiple ways of communicating with a single node. In identifying
this, it then determines the best way of communicating with that node
and blocks out the other paths.
Virtual local area networks (VLANs) A VLAN is a virtual LAN that is used
to allow computers and other network devices to appear as if they are on
the same network segment, regardless of where they are physically located.
Trunking Trunking refers to a single network link that allows multiple
VLANs to communicate with one another. Two switches can send and
receive the network traffic from two or more VLANs using a trunking
protocol.
Port mirroring Port mirroring is a process in which all the data sent or
received on one port or VLAN is copied to another port and is also known
as a Switched Port Analyzer (SPAN) or roving analysis port (RAP). This is
sometimes used to implement intrusion detection systems (IDSes).
Port authentication Port authentication is a process in which access to a
port is given to a device by having that device authenticate itself with a server
before communication over the port is allowed.
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The Modem and Other Adapters
The modem gets its name from a combination of the terms modulator and
demodulator. Modems can be categorized into three types:
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External modem is commonly used to provide connectivity between computers,
existing as a separate component that is attached to a computer
using a cable.