Cabling Best Practices

Version 1

    Cables should be treated with caution. In this post you can find the best practice guidelines for cabling your lab.

    References

     

    General Rules

    • Do not kink, twist or bend cables beyond the recommended minimum radius
    • Do not step, stand on or roll equipment over the cables
    • Avoid laying cables on the floor
    • Do not uncoil the cable, as a kink might occur. Hold the coil closed as you unroll the cable, pausing to allow the cable to relax as it is unrolled.
    • Plan cable paths away from foot
    • Do not pull the cable out of the shipping box, through any opening, or around any corners. Unroll the cable as you lay it down and move it through turns.
    • Do not twist the cable to open a kink. If it is not severe, open the kink by unlooping the cable.
    • Do not pack the cable to fit a tight space. Use an alternative cable route.
    • Do not hang the cable for a length of more than 2 meters (7 feet). Minimize the hanging weight with intermediate retention points.
    • Lay cables in trays as much as possible
    • Do not drop the cable or connectors from any height. Gently set the cable down, resting the cable connectors on a stable surface.
    • Do not cinch the cable with hard fasteners or cable ties. Use soft hook-and-loop fasteners or Velcro ties for bundling and securing cables.
    • Do not drag the cable or its connectors over any surface. Carry the entire cable to and from the points of connection.
    • Do not force the cable connector into the receptacle by pushing on the cable. Apply connection or disconnection forces at the connector only.

     

    Zero Tolerance for Dirt

    • With fiber optics, the tolerance of dirt is near zero. Airborne particles are about the size of the core of Single Mode fiber; they absorb a lot of light and may scratch connectors if not removed.
    • Try to work in a clean area. Avoid working around heating outlets, as they blow a significant amount of dust.
    • Dirt on connectors is the biggest cause of scratches on polished connectors and high loss measurements
    • Always keep dust caps on connectors, bulkhead splices, patch panels or anything else that is going to have a connection made with it

     

    Installation Precautions

    • Avoid over-bundling the cables or placing multiple bundles on top of each other. This can degrade performance of the cables underneath.
    • Keep copper and fiber runs separated
    • Do not place cables and bundles where they may block other equipment
    • Install spare cables for future replacement of bad cables – 2 per 100 cables
    • Do not bend the cable beyond its recommended radius. Ensure that cable turns are as wide as possible.
    • Do not staple the cables
    • Color code the cable ties, colors should indicate the endpoints. Place labels at both ends, as well as along the run.
    • Test every cable as it is installed. Connect both ends and make sure that it has a physical and logical link before connecting the next one.
    • Locate the main cabling distribution area in the middle of the data center
    • Avoid placing copper cables near equipment that may generate high levels of electromagnetic interference
    • Avoid runs near power cords, fluorescent lights, building electrical cables, and fire prevention components
    • Avoid routing cables through pipes and holes since this may limit additional future cable runs

     

    Daily Practice

    • Avoid exposing cables to direct sunlight and areas of condensation
    • Do not mix 50 micron core diameter cables with 62.5 micron core diameter cables on a link
    • When possible, remove abandoned cables that can restrict air flow causing overheating
    • Bundle cables together in groups of relevance (for example ISL cables and uplinks to core devices). This aids in management and troubleshooting.
    • Use cables of the correct length. Leave only a little slack at each end. Keep cable runs under 90% of the max distance supported for each media type as specified in the relevant standard.
    • Use Velcro based ties every 12" (30cm) to 24" (60cm)

     

    Labeling

    Labeling all cables between the leaf and the core switches is highly recommended. Failure to label the leaf-core cables hampers efforts to isolate, identify, and troubleshoot any potentially faulty cables when the cluster is deployed.

    It is important that all nodes in the cluster are individually named and labeled in a way that uniquely identifies them. There are several options for node naming; numerically, based on the size of the cluster (for example, node1023); physically, based on rack number (for example, nodeR10S5, for Rack10, Slot5); or topologically, based on location (for example, nodeL7P10, for leaf switch 7 port 10). There are advantages and disadvantages to each option.