Network Wiring– Cisco Basic Network Hardware

Every network engineer—at some point in their career, at least—runs network wiring, so it is essential to understand how to perform this fundamental task. Figure 10-9 illustrates cable management.

Figure 10-9 With and Without Cable Management The left side of Figure 10-9 shows a rack cabled without management aids, bundling, or even separation. The result is a tangled mess; seeing and replacing equipment is challenging. In contrast, on the right side of Figure 10-9 the operator cabled the rack neatly and spaced the equipment apart, using horizontal D-ring organizers to hold cables in neat horizontal rows.

As shown on the left side of Figure 10-9, cables hanging off their own connectors will strain their connectors. This strain can sometimes cause failures. While most commercially built cables will have strain gages (also spelled strain gauges) to reduce damage to internal connections, cable management techniques like those shown on the right side of Figure 10-9 can prevent failures of this kind.

Other kinds of  rack-mounted cable organizers include

• Vertical fingerboards

• Vertical lacing bars

• Vertical cable ladders

• Horizontal fingerboards

• Horizontal cable shelves

• Horizontal lacing bars

Cable management systems can take up rack space, so carefully plan the rack layout to include these elements. Raised floors have generally been abandoned in most designs for overhead cable racks, such as the one shown in Figure 10-10.

Figure 10-10 Overhead Cable Tray

Engineers must design overhead cable trays to carry the weight of the supported cables. Sometimes, this weight must be calculated into ceiling or rack weight loads.

Copper cables produce heat when power is running through them. Low-power Ethernet cables might not individually produce enough heat to cause damage, but large groups of cables bundled into a tray can. Because of this, heat is also a factor when designing an overhead cable tray system.

Some operators like to include loops in their optical cables, but loops should never be included in copper cables. Copper cables should be cut or commercially built as close to the length needed as possible. Loops add weight to the cable system, can act like antennas, or interfere with signal transmission.

You should use patch panels when wiring might frequently change, such as connecting network equipment to network wall jacks in a room or building. Patch panels can also be useful when cable lengths change while replacing equipment.

In summary, wiring to a physical network diagram is easy on the surface but more difficult if the job is to be done correctly.