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I'm getting notifications on my Syslog server from the Netgear switches GS748Tv4 and v5. These are the notifications:

traputil.c(696) 122305 %% Link Down: g30                                
traputil.c(696) 122323 %% Link Up: g30
traputil.c(739) 122307 %% Spanning Tree Topology Change: 0, Unit: 1
traputil.c(739) 122308 %% Spanning Tree Topology Change Initiated: 0, Interface: g30

Not only for the port g30 but for other ports as well. STP is enabled on both swithces. I don't know exactly what is causing this but when this happens, the user loses connection.

Any ideas?

Thank you,

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  • What does port g30 connect to?
    – David Schwartz
    Mar 22, 2016 at 22:21
  • I don't know yet but the same notifications for port g6, connects to a Windows 8 PC. The NIC is Gigabit but the status indicates 100 Mbps. I changed the settings from Auto Negotiation to 1Gbps Full duplex and the NIC couldn't connect. We recently upgraded out network with CAT 6 cables. All the cables from the wall jack to the computer are CAT 6 too.
    – Blake Zero
    Mar 23, 2016 at 0:30
  • You should never force 1Gbps unless you have know precisely what you are doing and have a very unusual situation. You should always use auto-negotiation. My guess is that whoever did your cat6 wiring messed up the mapping of pins to pairs. Carefully inspect the order of wires and make sure it's either 568A or 568B consistent throughout, straight through. 568B is preferred.
    – David Schwartz
    Mar 23, 2016 at 3:47

1 Answer 1

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Most likely, your category 6 wiring was done incorrectly. Carefully check the mapping of pins to wire pairs. I'll bet that it will not conform to either 568A or 568B. This is essential for Gigabit Ethernet to work correctly.

The preferred mapping is:

  1. Orange/White
  2. Orange
  3. Green/White
  4. Blue
  5. Blue/White
  6. Green
  7. White/Brown
  8. Brown

Also acceptable is:

  1. Green/White
  2. Green
  3. Orange/White
  4. Blue
  5. Blue/White
  6. Orange
  7. Brown/White
  8. Brown

The wiring should be the same at both ends of each cable. If this is not how the cables are wired, this is almost certainly your problem. If this mapping is incorrect, the twists in the cable will be unable to serve their function of preventing the four differential signals from interfering with each other.

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