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Checking a network cable/connection

  • Updated

 

Visual inspection

Cable

  • Check for any cuts/nicks in the cable. If any copper is visible this will lead to a faulty connection.
  • Check for anything crushing the cable or harsh bends, most are resilient but even if the outer shielding is intact there may be exposed copper inside

Ports

  • RJ45/Ethernet ports should look clean, with no sign of corrosion. If any of the contacts or surrounding area look blue/green this could indicate water damage.
  • Contacts should also be straight, not bent or peeled back. Finally connect an ethernet cable, it should ‘click’ in when pushed all the way. If it doesn’t click this could mean an obstruction in the port or damage from forceful removal.
  • Some switchports aren’t PoE, and this can be split across a switch or disabled in configurations. Connect with a cable and camera or PoE device you know works, if it fails to power on this might indicate an issue.

Plug

  • RJ45 plugs without clip tabs can still function, but it’s advisable to replace as they can fall out without the fixing mechanism.
  • Inspect the contacts at the end of the plug, all small cables should reach the end of the plug and be stamped though by both prongs of a contact. If any cables crossing over, touching or not reaching the contacts the cable won’t function properly.
  • Also assure the small cables are in the correct order, holding the plug with the tab facing away cables should be ordered;
    • White/Orange
    • Orange
    • White/Green
    • Blue
    • White/Blue
    • Green
    • White/Brown
    • Brown
  • The outer cable sleeving should be fully seated in the plug, if any of the small cables are exposed this can lead to damage.

Patch panels & Wall ports

Similar to plugs, all cables should be properly connected to a patch panel or wall port. When removing from situ to check always do so carefully as the cables might be short and pulling on them can create further issues.

  • Usually there is a guide behind the cables indicating where these should be located, if connected in a straight line this is the same as the plug order.
  • Check all small cables have been properly ‘punched down’ the small cable end should be sandwiched between the contacts and snipped flush.

Cable Tester

Using a cable tester can quickly identify any issues with crimping at the end of a cable or identify damage along the line of a cable.

  • Most cable testers can alert when a ‘pair’ is not working, if this occurs check the contacts at both ends. If the ends seem fine this might indicate a damaged cable.
  • Some cable testers can test distance, if you know the approximate distance of a cable and the tester reports much shorter then it is highly likely the cable is damaged.
  • If a cable tester reports a ‘short’ on the line this might indicate a damaged cable. HOWEVER, a short could also be reported if the other end of the cable is connected to a live network port.

ETHERNET CABLE IS NOT ELECTRICAL CABLE

  • Ends cannot be spliced by twisting & taping a correct coupler needs to be used
    • Both ends should be crimped and attached with a RJ45 coupler
    • A very quick fix is jelly connectors, but this should only be done as a last resort and care taken to match colours, preserve twists and protect the exposed cables.
  • Any exposed copper will lead to cross talk and transmission issues.
  • All internal cables must function, there is no redundant lines.
  • Never strip the coating from internal cables, connections are made through contact teeth punching through.
  • Only crimp a RJ45 plug with proper crimping tools, never push contacts with a screwdriver or other tool.
  • When stripping outer sleeving, assure the internal cables aren’t nicked.