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

Network Devices 39
Bridges
Bridges have the capability to forward packets of data based on MAC addresses.
A bridge can look at a packet of data and determine the source and destination
involved in the transfer of packets. It will read the specific physical address of
a packet on one network segment and then decide to filter out the packet or
forward it to another segment. A bridge is a simple way to accomplish network
segmentation. Bridges segment the network by MAC addresses.
EXAM WARNING
Bridges operate at the data link layer, Layer 2, of the OSI model and use physical addressing
to join several networks into a single network efficiently.
Multistation Access Units
Multistation access units (also known as MAUs or MSAUs) are used to connect
workstations on a Token Ring network. A MAU typically has eight or more ports
that provide connections for workstations and other network devices on a Token
Ring network.
Crunch Time
Convergence occurs when vendors put many features into
one device. As time goes on, you can expect to see other
devices converging together, requiring networks to have
fewer components. When you are taking the Network+
exam, it is wise to consider such devices as separate,
rather than as one device providing all features. For example,
even though your router for the Internet has a firewall,
you should consider a router and a firewall as two separate
components of a network when taking the exam.
Understanding Switches
A switch stores Layer 2 address information (MAC addresses) regarding each host
connected to it. When a frame sent from a host attached to the switch enters the
switch port, the switch reads through the MAC address information to determine
which port the destination host is attached to and then sends the frame out that
port. The only time a switch will send out the data to all of its ports is when a
broadcast message is sent.
Broadcast messages are messages that are sent out to all the nodes in a broadcast
domain. While the basic functionality of a switch is similar to a hub, there are
some fundamental differences. Switches offer full-duplex dedicated bandwidth
to local area network (LAN) segments or desktops. You can think of a switch as
an intelligent hub that guarantees a specific amount (10, 100, or 1000 Mbps) of
bandwidth to the computer that it is connected to. With a hub, you are guaranteed