Fiber Backbone, Unshielded Twisted Pair to-the-Desk
Configuring a network with unshielded twisted pair cabling to-the-desk is similar to an all-fiber network because the cabling is star-wired in both cases.
Be aware of the following additional rules for configuring a network:
❑The four-repeater rule in Ethernet limits the number of 10BASE-T modules between any two transceivers. The path from the TP port to the backplane counts as 1/2 of a repeater and the path from the backplane to the TP port counts as 1/2 of a repeater. You must add a bridge if the path from one transceiver to another exceeds the four-repeater rule.
❑The equivalent fiber distance for the 10BASE-T Modules is defined in “Understanding Network Configuration” in this chapter:
–420 meters for signals that externally enter a 10BASE-T Module port
–165 meters for signals that internally enter a 10BASE-T Module through the ONline concentrator backplane
For each pair of 10BASE-T Modules that a signal goes through, there is a fiber equivalent distance of 585 meters (420 m + 165 m =585 m). In addition, if a signal makes a roundtrip through a 10BASE-T Module, (that is, enters a 10BASE-T port externally and exits through another port on the same 10BASE-T Module) that counts as 585 meters of fiber equivalent distance, and as a full repeater.
Example: Sample Configuration Distance Calculation
Use the following example to determine if the 10BASE-T Transceivers in Figure are within legal Ethernet limits. Identify the two transceivers that are likely to be the greatest fiber equivalent apart in Figure 2-8. In this case, they are 10BASE-T Transceivers A and B.
2 - 22 ONline Ethernet 10BASE-FB Module Installation and Operation Guide