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Cabling Guidelines
B-1
202-10088-01, March 2005
Appendix B
Cabling Guidelines
This appendix provides specifications for cables used with a NETGEAR NETGEAR 7300S Series
Layer 3 Managed Switch.
Fast Ethernet Cable Guidelines
Fast Ethernet uses UTP cable, as specified in the IEEE 802.3u standard for 100BASE-TX.The
specification requires Category 5 UTP cable consisting of either two-pair or four-pair twisted
insulated copper conductors bound in a single plastic sheath. Category 5 cable is certified up to
100 MHz bandwidth. 100BASE-TX operation uses one pair of wires for transmission and the
other pair for receiving and for collision detection.
When installing Category 5 UTP cabling, use the following guidelines to ensure that your cables
perform to the following specifications:
Certification
Make sure that your Category 5 UTP cable has completed the Underwriters’ Laboratories (UL) or
Electronic Testing Laboratories (ETL) certification process.
Termination method
To minimize cross-talk noise, maintain the twist ratio of the cable up to the point of termination;
untwist at any RJ-45 plug or patch panel should not exceed 0.5 inch (1.5 cm).
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User Manual for the NETGEAR 7300S Series Layer 3 Managed Switch Software
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Cabling Guidelines
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Category 5 Cable
Category 5 distributed cable that meets ANSI/EIA/TIA-568-A building wiring standards can be a
maximum of 328 feet (ft.) or 100 meters (m) in length, divided as follows:
20 ft. (6 m) between the hub and the patch panel (if used)
295 ft. (90 m) from the wiring closet to the wall outlet
10 ft. (3 m) from the wall outlet to the desktop device
The patch panel and other connecting hardware must meet the requirements for 100 Mbps
operation (Category 5). Only 0.5 inch (1.5 cm) of untwist in the wire pair is allowed at any
termination point.
Category 5 Cable Specifications
Ensure that the fiber cable is crossed over to guarantee link.
The Table below lists the electrical requirements of Category 5 UTP cable.
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User Manual for the NETGEAR 7300S Series Layer 3 Managed Switch Software
Cabling Guidelines
B-3
202-10088-01, March 2005
Table 12-4.
Electrical Requirements of Category 5 Cable
Twisted Pair Cables
For two devices to communicate, the transmitter of each device must be connected to the receiver
of the other device. The crossover function is usually implemented internally as part of the
circuitry in the device. Computers and workstation adapter cards are usually media-dependent
interface ports, called MDI or uplink ports. Most repeaters and switch ports are configured as
media-dependent interfaces with built-in crossover ports, called MDI-X or normal ports. Auto
Uplink technology automatically senses which connection, MDI or MDI-X, is needed and makes
the right connection.
Figure 12-3
illustrates straight-through twisted pair cable.
Figure 12-3:
Straight-Through Twisted-Pair Cable
SPECIFICATIONS
CATEGORY 5 CABLE REQUIREMENTS
Number of pairs
Four
Impedance
100 ± 15%
Mutual capacitance at 1 KHz
5.6 nF per 100 m
Maximum attenuation
(dB per 100 m, at 20° C)
at 4 MHz: 8.2
at 31 MHz: 11.7
at 100 MHz: 22.0
NEXT loss (dB minimum)
at 16 MHz: 44
at 31 MHz: 39
at 100 MHz: 32
Page 374 / 400
User Manual for the NETGEAR 7300S Series Layer 3 Managed Switch Software
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Cabling Guidelines
202-10088-01, March 2005
Figure 12-4
illustrates crossover twisted pair cable.
Figure 12-4:
Crossover Twisted-Pair Cable
Patch Panels and Cables
If you are using patch panels, make sure that they meet the 100BASE-TX requirements. Use
Category 5 UTP cable for all patch cables and work area cables to ensure that your UTP patch
cable rating meets or exceeds the distribution cable rating.
To wire patch panels, you need two Category 5 UTP cables with an RJ-45 plug at each end, as
shown here.
Figure 12-5:
Category 5 UTP Cable with Male RJ-45 Plug at Each End
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User Manual for the NETGEAR 7300S Series Layer 3 Managed Switch Software
Cabling Guidelines
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202-10088-01, March 2005
Note
: Flat “silver satin” telephone cable may have the same RJ-45 plug. However, using telephone
cable results in excessive collisions, causing the attached port to be partitioned or disconnected
from the network.
Using 1000BASE-T Gigabit Ethernet over Category 5 Cable
When using the new 1000BASE-T standard, the limitations of cable installations and the steps
necessary to ensure optimum performance must be considered. The most important components in
your cabling system are patch panel connections, twists of the pairs at connector transition points,
the jacket around the twisted-pair cable, bundling of multiple pairs on horizontal runs and punch
down blocks. All of these factors affect the performance of 1000BASE-T technology if not
correctly implemented. The following sections are designed to act as a guide to correct cabling for
1000BASE-T.
Cabling
The 1000BASE-T product is designed to operate over Category 5 cabling. To further enhance the
operation, the cabling standards have been amended. The latest standard is Category 5e, which
defines a higher level of link performance than is available with Category 5 cable.
If installing new cable, we recommend using Category 5e cable, since it costs about the same as
Category 5 cable. If using the existing cable, be sure to have the cable plant tested by a
professional who can verify that it meets or exceeds either ANSI/EIA/TIA-568-A:1995 or ISO/
IEC 11801:1995 Category 5 specifications.
Length
The maximum distance limitation between two pieces of equipment is 100 m, as per the original
Ethernet specification. The end-to-end link is called the “channel.”
TSB-67 defines the “Basic Link” which is the portion of the link that is part of the building
infrastructure. This excludes patch and equipment cords. The maximum basic link length is 295
feet (90 m).
Return Loss
Return loss measures the amount of reflected signal energy resulting from impedance changes in
the cabling link. The nature of 1000BASE-T renders this measurement very important; if too much
energy is reflected back on to the receiver, the device does not perform optimally.

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