52 GLOSSARY
loop An event that occurs when two network devices are connected by
more than one path, thereby causing packets to repeatedly cycle
around the network and not reach their destination.
MAC Media Access Control. A protocol specified by the IEEE for determining
which devices have access to a network at any one time.
MAC address Media Access Control address; also called hardware or physical address.
A layer 2 address associated with a particular ne twork devi ce. Most
devices that connect to a LAN have a MA C address assigned t o them
as they are used to identify other devices in a network. MAC addresses
are 6 bytes long.
MDI Medium Dependent Interface. An Ethern et port conn ection where t he
transmitter of one device is connected to the receiver of another
device.
MDI-X Medium Dependent Interface Cross-over. An Ethernet port connect ion
where the internal transmit and receive lines are crossed.
multicast A packet sent to a specific group of endstations on a network.
NIC Network Interface Card. A circuit board installed in an endstation that
allows it to be connected to a network.
POST Power On Self Test. An internal test that a Switch carries out when it is
powered-up.
protocol A set of rules for communication between devices on a ne twork. The
rules dictate form at, ti ming , sequ enci ng a nd er ror co ntrol.
repeater A simple device that regen erate s LA N traffi c so t hat the tr ansm issio n
distance of that signal can be extended. Repeaters are used to connect
two LANs of the same network type.
router A device that provides WAN links b etween g eographicall y separate
networks.
RPS Redundant Power System. A device that provides a b ackup source of
power when connected to a Switch.
segment A section of a LAN that is connected to the rest of the network using a
switch or bridge.
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