Device Configuration Tool: Network Jack Troubleshooting


This document outlines basic troubleshooting steps for an ethernet jack that was previously confirmed as working. If you are trying to plug a machine into a network jack that has never been used before and are not getting a signal, refer to Activate a Port to get the jack activated.

Symptom 1: No Physical Connection

If the user is not getting any signal on its ethernet port, the issue is with physical wiring. The following symptoms indicate no physical connection:

  • On a PC, when you click on Control Panel -> Network the "LAN" or "Ethernet Adapter" says "Network Cable Unplugged".
  • On a MAC, when you click on System Preferences -> Network -> and look for the Ethernet line item, it says "Not Connected" underneath.

If you see no physical connection, try plugging the machine into a jack you know is working (using the same ethernet cable.

  • If the machine starts working, open a ticket with ITS - Service Center -> ITS NOC Network Operation Center and request that a field technician come out and troubleshoot the bad jack.
  • If the machine does not work when plugged into a good jack, swap out the ethernet cable for one you know is working.
  • If swapping out the ethernet cable does not work, there must be something wrong with the machine itself (since you are using a jack and an ethernet cable you know are good).

Symptom 2: Physical Connection Detected, No Network Functionality

If the user is seeing a physical connection but the network is not working, most likely they are on the wrong VLAN. You should be able to use DCT to put them on the right VLAN, here is how:

  1. Obtain the user's MAC address
  2. On your own machine, browse to the Device Configuration Tool (DCT). Enter the MAC address the "end user device" field, select your building, and click "Submit".
  3. The port that the user is on should pop up and show what VLAN the user is on. Click anywhere on the port information to change the VLAN if applicable.

If DCT does not find the user's MAC address or your building is not listed in the dropdown, you can use a fluke (if you have one) to figure out the VLAN and switch port that the user is on (reference How to Use A Fluke Network Tool).

  1. If the user is on the correct VLAN, make sure their network card is configured for DHCP (or for their static address) as appropriate.
  2. If the user is not on the correct VLAN (or you can't figure out what VLAN they are on) and you cannot fix it via DCT, submit a help request ticket and assign to ITS - Network. Please include all information gathered during troubleshooting (MAC address, switch and port). For immediate assistance during business hours you can also call 734-647-4200.

Symptom 3: Intermittent Network Connectivity

If the user's connection is intermittent - for example, web pages half load, or the computer reports "no connectivity" every couple of minutes, it's possible that there is a speed/duplex mismatch, or that the wiring is faulty or too old to handle gigabit ethernet.

  1. Find the user's switchport in DCT and check for errors (the last two columns of the interface output).
  2. If you see a large amount of errors (like in the hundreds or thousands), load the page again. If the errors are incrementing, that indicates there are problems with the link. Make sure the speed and duplex settings are the same on the switchport as on the user's machine.
  3. If you have verified speed/duplex settings and errors persist and you are in an older building with Cat3 wiring, try setting the speed and duplex to be 100/full or 10/full. Most likely you'll see other ports on the switch set this way if the building wiring is old.
  4. If errors still persist over newer cabling, try replacing the cable. If that doesn't work, submit a help request ticket and assign to ITS - Service Center -> ITS NOC Network Operation Center and request that a field technician come out and troubleshoot the bad jack.
  5. If you do not see errors on the port, try moving the user to a known working jack (or if you don't have one nearby, try a known working machine on the suspect jack). If your testing still implicates the jack, follow Diagnosing Slow Network Performance to determine the scope of the issue and to obtain appropriate diagnostic information. Put that information into a help request ticket and assign to ITS - Network.
Last Updated: 
Wednesday, January 4, 2017