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Appendix D Commonly Asked Questions 21
KNE24TX/RS User’s Guide - Rev. A01 Kingston Technology Company
Appendix D Commonly Asked Questions
Class
I
vs. Class
II
100BASE-TX Fast Ethernet
Repeaters
There are currently two classes of Fast Ethernet repeaters, defined as Class
I
and
Class
II
.
Class
I
: in a maximum length segment topology, only one Class
I
repeater may exist between any two nodes within a single
collision domain.
Class
II
: in a maximum length segment topology, two Class
II
repeaters may exist between any two nodes within a single collision
domain.
Will 100BASE-TX run on Category 3 cable?
No! Category 3 (CAT 3) cabling even in short lengths generates too much near
end crosstalk for 100BASE-TX networks. The IEEE 802.3u 100BASE-TX Fast
Ethernet standard requires Category 5 100 Ω UTP or 150 Ω STP which
complies with ISO/IEC 11801:1995.
What is Category 5?
Category 5 (CAT 5) is a further extension of the EIA/TIA-568 cabling system
to 100 MHz. Category 5 components (i.e., UTP trunk and patch cables,
modular plug, and patch panel, etc.) are defined by EIA/TIA-568, but with the
characterizations extended to 100 MHz by TSB-36 and TSB-40. The cable
grades are categorized as follows:
• Category 3: up to 16 MHz
• Category 4: up to 20 MHz.
• Category 5: up to 100 MHz.