What makes a fabric port change to a loop port?

If ports in your storage-area network switch are changing without updates, you need to examine the fabric device and loop device, and check to see if any drives may have been improperly connected.

Ports on my Brocade 4100 Switch have been changing from fabric ports to loop ports. Why is this happening?
First, you need to understand that switch ports in the Brocade 4100 for a storage-area network (SAN) environment should not change their topology without some kind of known event taking place. If no configuration changes have been made and ports are changing topology in a seemingly random manner, then a support call with Brocade should be opened.

It is possible that ports are changing from fabric to loop mode because one of the following events has occurred:

  • A previously empty switch port has had a loop device, such as a tape drive, connected to it.
  • A connected device has had its topology changed from fabric mode to loop mode.
  • A fabric device has been removed from the switch port and has been replaced with a loop device.

The above scenarios are all dependant on the switch ports being in auto-sensing mode. If the ports are fixed to a certain topology and one of the above takes place, the switch ports will need to be manually altered to enable the switch to talk to the connected device.

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