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Chapter 11
Troubleshooting Switched Ethernet
Cabling Issues
T
oday's networks operate at higher speeds than ever before. Bandwidth
is measured in gigabits, with individual workstations accessing 100Mb con-
nections or faster. Only recently it was still common to find a hundred stations
sharing a 10Mbit segment.
Higher speeds bring added complexity at the Physical layer of the net-
work. Installations must adhere to strict tolerances regarding distance, cable
type, and installation to permit proper operation. This creates new trouble-
shooting issues for the administrator.
Frequently, an administrator will convert a workstation to 100Mbit (Fast)
Ethernet, and will find an excessive number of errors that degrade perfor-
mance so much that the link becomes unusable. The type of cable or the dis-
tance between the switch and workstation may cause this. For example,
perhaps the original installation used Category 3 cable. Although satisfactory
for 10Mbit Ethernet, 100Mbit Ethernet requires the higher-capacity Category
5. Also, although the distance for both 10- and 100Mbit Ethernet on copper
media is 100 meters, it is possible to use longer lengths for 10Mbit without
degradation. When converting to 100Mbit, problems may become evident.
Consideration of the Physical layer is imperative when troubleshooting
switched networks. Table 11.5 presents the Physical layer limitations.
T A B L E 1 1 . 5
Physical Layer Standards
Cable
10Mbit
100Mbit
Distance with Category
3 copper
100 meters
Not available per
100BaseTX standard
Distance with Category
5 copper
100 meters
100 meters
Distance with Multi
Mode fiber
2,000 meters
2,000 meters
Distance with Single
Mode fiber
10,000 meters
10,000 meters
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