9.3 Components Used For a 100-Mbps Connection
Note that Ethernet ports on repeaters do not use an Ethernet interface. A repeater port connects to the Fast Ethernet media system using the same PHY and MDI equipment. However, repeater ports operate at the individual bit level for Ethernet signals, moving the signals directly from segment to segment. Therefore, repeater ports do not contain Ethernet interfaces since they do not operate at the level of Ethernet frames.
On the other hand, a repeater hub may be equipped with an Ethernet interface to provide a way to communicate with the hub over the network. This allows a vendor to provide a management interface in the hub that can interact with a remote management station, using the Simple Network Management Protocol (SNMP). Managed hubs make it possible for a network manager to remotely monitor the traffic levels and error conditions on hub ports, and to shut off ports for troubleshooting, etc.
There are two kinds of repeaters in the 100BASE-T system: Class I and Class II. The standard requires that Fast Ethernet repeaters be labeled with the Roman number "I" or "II" centered within a circle. The difference between these repeaters is described in the following media chapters.
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