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This chapter provides cabling guidelines for determining how to build networks using FastHubs and describes how to connect the FastHub to network devices.
The IEEE 802.3u standard defines two different classes of 100BaseT repeaters, Class I and Class II. Networks using Class I repeaters are limited to a single repeater (or stack). Class II repeaters allow networks to be built with more than one repeater (or stack). In addition, Class II repeaters allow longer cable distances in single repeater configurations than do Class I repeaters. The FastHub is a Class II repeater. Moreover, the FastHub exceeds the specifications for Class II repeaters, allowing the use of longer cable lengths than standard Class II repeaters.
The IEEE 802.3u standard specifies four simple network configurations using Class II repeaters. These configurations were designed to satisfy the requirements of most networks that are built to the EIA/TIA-568 wiring standard. This standard specifies 100-meter Category 5 UTP connections from wiring closets to desktops. If your network requirements cannot be met with one of these configurations, or if you are building networks mixing FastHubs with other Class II repeaters, see the "Extended and Multivendor Configurations" section in this chapter.
Configuration 1: Single FastHub, Only Cat 5 UTP Cable Segments
With only Cat 5 UTP cable segments, the maximum length for any cable segment is 100 meters, as shown in Figure 3-1.
Figure 3-1 : Single FastHub, Only Cat 5 UTP Cable Segments Configuration 2: Single FastHub, Cat 5 UTP Segments and One Fiber-Cable Segment
The maximum Cat 5 UTP cable segment length is 100 meters (see Figure 3-2).
The maximum fiber-cable segment length is 218 meters.
If all of the Cat 5 UTP-cable segments connected to the FastHub are less than 100 meters, the length of the fiber cable segment can be increased. See the "Extended and Multivendor Configurations" section for more information.
Figure 3-2 : Single FastHub, Cat 5 UTP Segments and One Fiber-Cable Segment Configuration 3: Two FastHubs, Only Cat 5 UTP Cable Segments
The maximum Cat 5 UTP cable segment length is 100 meters.
With 100-meter Cat 5 UTP cable segments connecting the stations to the FastHubs, the Cat 5 UTP cable connecting the two FastHubs is limited to a distance of 23 meters, as illustrated in Figure 3-3.
If all of the Cat 5 UTP cable segments connecting stations to one or both of the FastHubs are less than 100 meters, the length of the Cat 5 UTP cable segment connecting the two FastHubs can be increased. See the "Extended and Multivendor Configurations" section for more information.
Figure 3-3 : Two FastHubs, Only Cat 5 UTP Cable Segments Configuration 4: Two FastHubs, Cat 5 UTP Cable Segments and One Fiber-Cable Segment
With 100-meter Cat 5 UTP cable segments connecting the stations to the FastHubs and a 5-meter Cat 5 UTP cable connecting the two FastHubs, the maximum length fiber-cable segment length is 131 meters, as illustrated in Figure 3-4.
If all of the Cat 5 UTP cable segments connecting stations to the FastHub are less than 100 meters, the length of the fiber-cable segment or the length of the Cat 5 UTP cable segment connecting the two FastHubs can be increased. See the "Extended and Multivendor Configurations" section for more information.
Figure 3-4 : Two FastHubs, Cat 5 UTP Cable Segments and One Fiber-Cable Segment Extended and Multivendor Configurations
The previous cabling examples applied to configurations of one or two FastHub stacks with Cat 5 UTP segments assumed to be at their worst case distance, 100 meters. When the maximum Cat 5 UTP segment length is less than 100 meters, longer fiber segments, longer inter-repeater links, or more repeaters can be deployed. On the other hand, when FastHubs are deployed with standard Class II repeaters (Class II repeaters that meet but do not exceed the IEEE 802.3u specification), the maximum span is decreased.
A specific calculation of maximum cable length is required in the following cases:
Allowable repeater configurations are determined by the longest path between any two stations. This path constraint is determined by cable segment lengths, cable types, number of repeaters, and repeater types. The arithmetic underlying this determination can be reduced to a constraint on the sum of the segment lengths between the two furthest stations. The constraint is expressed in total meters and assumes that all segments are Cat 5 UTP. Therefore, fiber segments must be converted to their Cat 5 UTP equivalents.
Table 3-1 : Determining Cable Lengths
Example 1: Achieving Longer Fiber Connections
In this example, a 250-meter fiber segment is required to connect a FastHub to a server located 250 meters away. What are the maximum permissible Cat 5 UTP station connections in this configuration (see Figure 3-5)?
Figure 3-5 : Achieving Longer Fiber Connections Perform the following steps to determine the maximum permissible Cat 5 UTP cable segment lengths:
Example 2: Increasing the Distance Between Two FastHubs
It is possible to increase the distance between two FastHubs by reducing the maximum cable segments connecting stations to the FastHubs. Using Table 3-1, we see that the maximum Cat 5 UTP equivalent distance between any two stations separated by two FastHubs is 223 meters.
In the following example, it is necessary to separate the two repeaters by 120 meters (see Figure 3-6). First, since this distance is greater than 100 meters, we must use fiber cable. Convert the fiber distance to its UTP equivalent by multiplying by 0.9. This gives us a UTP equivalent of 108 meters (120 x 0.9 = 108 meters). Using A + B + C = 223 meters and substituting 108 meters for segment B, we arrive at A + C £ 115 meters.
Figure 3-6 : Increasing the Distance Between Two FastHubs Example 3: Adding a Third FastHub Stack
It is possible to add a third FastHub stack in the same collision domain to increase the total number of connected stations to 380. Using Table 3-1, we see that the maximum Cat 5 UTP equivalent distance between any two stations connected by three FastHubs is 149 meters.
In the following example, all three hub stacks are in the same wiring closet, separated by
Note that after assigning cable lengths to A and E, we must check to see if the configuration rules for stations separated by two FastHubs have been violated. That is, A + B + C
To satisfy both paths (A, B, C and C, D, E), C must be less than or equal to 135 meters. Note that these are Cat 5 UTP equivalent meters. If fiber cable is used, C must be £ 135 x 1.11, or C £ 150.
Figure 3-7 : Adding a Third FastHub Stack Example 4: One FastHub and One Other Class II Repeater
It is possible to build networks combining FastHubs with other Class II repeaters from Cisco or other vendors (see Figure 3-8).
Using Table 3-1, we see that A + B + C £ 214 meters. Note that these are Cat 5 UTP equivalent meters.
Figure 3-8 : One FastHub and One Other Class II Repeater This section provides procedures to connect devices to the 100BaseTX and 100BaseFX ports.
The 100BaseTX ports are compatible with the 100BaseTX IEEE-802.3u specification and can connect to any 100BaseTX device.
All FastHub 100BaseTX ports use RJ-45 type connectors and require Cat 5 UTP cable (see Figure 3-9). The 100BaseTX ports (excluding the uplink port, port 16) are internally crossed, enabling the use of straight-through cables when connecting to a server or workstation. Attached servers or workstations must have a 100BaseTX-compatible adapter installed. When using the 100BaseTX ports (excluding the uplink port) to connect to another hub, switch, or router, a crossover cable must be used (unless you are connecting to the uplink port on another FastHub or 100BaseT hub).
The 100BaseTX uplink port is not internally crossed, enabling the use of standard straight-through cable when connecting to another FastHub 100BaseTX port or to the 100BaseTX port on another hub, switch, or router. Note that the port on the device you are connecting to must be an X port.
See "Connectors and Cabling" in Appendix B for connector pinouts.
Figure 3-9 : Making Port Connections: 100BaseTX Ports Warning Avoid exposure to the laser beam.
The 100BaseFX ports are compatible with the 100BaseFX IEEE-802.3u specification and can connect to any 100BaseFX device.
The FastHub 116C+ 100BaseFX port uses an SC type connector and requires 62.5/125- or 50/125-micron multimode, fiber cable (see Figure 3-10). The 100BaseFX port can be used to connect to compatible ports on switches, routers, or other hubs. Attached servers or workstations must be equipped with a 100BaseFX adapter.
Figure 3-10 : Making Port Connections: 100BaseFX Port If there is no link activity, the port LEDs are on (solid green). This shows that the FastHub and the connected devices are turned on and that the link is operational with no activity.
If there is link activity, the port LEDs are on (flashing green). This shows that the FastHub and the connected devices are turned on and that the link is operational with activity.
If the port LEDs are on and alternating green/amber, a reset is in progress.
If the port LEDs are on and rapidly alternating green/amber or are solid amber, see the "Troubleshooting" chapter to determine the source of the problem.
If the port LEDs are off, the FastHub or connected devices are not powered on, or the cable is incorrectly wired.
Copyright 1988-1996 © Cisco Systems Inc.
In any configuration, the maximum Category 5 UTP cable length (hereafter referred to as Cat 5 UTP) is 100 meters. Longer segment lengths are possible only when using multimode fiber-optic cable (hereafter referred to as fiber cable).
Number and Type of Repeaters
in the Path
Maximum Total Cable Distance in Path
(Cat 5 UTP Equivalents)
1 FastHub
296
1 other Class II repeater
287
2 FastHubs
223
1 FastHub and 1 other Class II repeater
214
3 FastHubs
149
2 FastHubs and 1 other Class II repeater
140
1 FastHub and 2 other Class II repeaters
131
1-meter Cat 5 UTP cable segments. Substituting back into the formula shown in Figure 3-7, we see that A + E £ 147 meters. If A is 60 meters, then E would be 87 meters.
£ 223 meters and C + D + E £ 223 meters. For the first configuration, we get: A (60 meters) + B (1 meter) + C £ 223. In this case, C must be £ 162. For the second configuration (C + D + E £ 223) we get: D (1 meter) + E (87 meters) + C £ 223. In this case, C must be £ 135.
