Dual-Speed Stackable Hubs User’s Guide
Hub Types
Unlike 10BASE-T hubs, which are all functionally identical, Fast Ethernet hubs are divided into two distinct types: Class I and Class II. A Class I hub repeats all incoming signals on one port to the other ports by first translat- ing them to digital signals and then retranslating them back to line signals. These translations are necessary when connecting various network media to the same collision domain, such as when combining two wire-pair 100BASE-TX media with four wire-pair 100BASE-T4 media. Only one Class I hub can exist within the same collision domain; thus, this type of hub cannot be directly interlinked. A Class II repeater, on the other hand, immediately repeats all incoming line signals on one port to the other ports; no translations are performed. This type of hub connects identical media within the same collision domain; for example, TX to TX. At most, two Class II hubs can exist within the same collision domain.
As mentioned earlier, stackable Class II hubs can be used to increase the number of available nodes in a collision domain. An entire hub stack counts as a single repeater. DFE-908 series hubs are Class II devices.
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UNPACKING AND
SETUP
This chapter provides information on the unpacking and initial installation of your hub stack.