3Com Baseline 2848-SFP Plus User Manual

Also see for 2848 SFP - Baseline Switch Plus: Datasheet Release note

Contents

46 TROUBLESHOOTINGA link is connected but the Link/Activity Status LEDfor the port does not lightThere is a problem with this connection. Check that:■ The device being connected to is powered on andoperating correctly.■ The cable is connected at both ends.■ The cable is not damaged.■ If the connection is to a workstation, that theworkstation's network interface is installed andconfigured correctly.■ The correct category of cable is being used for therequired link speed. Category 3 cable can be usedfor 10BASE-T operation only. Category 5 cable isrequired for 100BASE-TX or 1000BASE-T. 3Comrecommends Category 5e or 6 cable for 1000BASE-Toperation.A fiber cable is connected but the Module PresentLED does not lightCheck that:■ The Receive (RX) and Transmit (TX) cable connectorsare not swapped.■ The fiber cable is in good condition.■ The SFP module is correctly inserted.■ A 3Com SFP module is being used. Refer to“Approved SFP Transceivers” on page 17 for details.■ The equipment at the far end is installed andcorrectly configured.The Link/Activity LED is lit but the networkperformance of the Switch is poorThe Switch supports full-duplex auto-negotiation. If theconnected device does not support auto-negotiation,ensure it is configured for half-duplex operation only. Ifthe connected device has auto-negotiation disabled orover-ridden, and is configured as full duplex, the Switchwill configure the link as half duplex, causing amis-match that will reduce network performance whendata is transmitting and receiving simultaneously on thesame link.Ensure that the connected device has either:■ Auto-negotiation enabled, or■ The ports are configured for half-duplex operationAll ports appear to show continual activityThere may be broadcast storms on the network.Remove port connections one at a time, waiting a fewseconds between each port. If the LEDs go off afterremoving a port connection, the device that wasconnected to that port is introducing an excessiveamount of broadcast frames to the network (somepieces of network equipment operate by sending outbroadcast frames regularly). Refer to the documentationthat accompanies the device for information ondisabling the broadcast operation.