3Com 9100 manual No link light on Gigabit fiber port, VLANs You cannot add a port to a Vlan

Using the Command-Line Interface 153

A mismatch of duplex mode between the Switch 9100 and the network device will cause poor network performance. Viewing using the show port rx command on the Switch 9100 may display a constant increment of CRC errors. This is characteristic of a duplex mismatch between devices. This is NOT a problem with the switch.

Always verify that the switch and the network device match in configuration for speed and duplex.

No link light on Gigabit fiber port:

Check to ensure that the transmit fiber goes to the receive fiber side of the other device, and vice-versa. All gigabit fiber cables are of the cross-over type.

The Switch 9100 has auto-negotiation set to on by default for gigabit ports. These ports need to be set to auto off (using the command config port <port #> auto off) if you are connecting it to devices that do not support auto-negotiation.

Ensure that you are using multi-mode fiber (MMF) when using a 1000BASE-SX port. 1000BASE-SX does not work with SMF.

VLANs You cannot add a port to a VLAN:

If you attempt to add a port to a VLAN and get an error message similar to

localhost:7 # config vlan marketing add port 1,2

ERROR: Protocol conflict on port 5

you already have a VLAN using untagged traffic on a port. Only one VLAN using untagged traffic can be configured on a single physical port.

VLAN configuration can be verified by using the following command:

show vlan <name>

The solution for this error is to remove ports 1 and 2 from the VLAN currently using untagged traffic on those ports. If this were the “default” VLAN, the command would be

localhost:23 # config vlan default del port 1,2