11.3 100BASE-FX Configuration Guidelines

The 100BASE-FX Ethernet segments are defined as link segments in the Ethernet specifications. A link segment is formally defined as a point-to-point medium that connects two and only two MDIs. The smallest network built with a link segment would consist of two computers, one at each end of the link segment.

TABLE 11.1 100BASE-FX segment configuration guidelines

A more typical installation uses multiport repeater hubs or packet switching hubs, to provide a connection between a larger number of link segments. You connect the Ethernet interface in your computer to one end of the link segment, and the other end of the link segment is connected to the hub. That way you can attach as many link segments with their associated computers as you have hub ports, and the computers all communicate via the hub.

Note that while a single 10BASE-FX segment may be up to 412 meters in length, when repeaters are used the maximum distance between DTEs will be less. If a single Class II repeater is used to link fiber segments, then the maximum distance between any two DTEs linked with all fiber segments may be 320 meters. This maximum distance is also called the maximum collision domain diameter. If a single Class I repeater is used, then the maximum distance between DTEs linked with all fiber segments may be 272 meters. Finally, if two Class II repeaters are used the maximum distance between two DTEs linked with all fiber segments may be 228 meters.

The configuration rules for mixing 100 Mbps segment types and repeater types together are described in the chapter on Fast Ethernet multi-segment configuration guidelines.

Quick Reference Guide to 100BASE-FX - 09 SEP 95

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