Configuring UplinkFast
What is a link fault?

In STP, a link fault is the loss of connectivity on a port directly connected to the switch. A link fault will occur on a switch root port. Loss of connectivity is determined by the absence of BPDUs on the link providing access to the root switch.

A link fault can occur as a result of the following:

  • The media toward the root switch is physically disconnected
  • The media toward the root fails
  • The switch port at the other end of the root port fails, is disabled or is shutdown
  • Any event in software or hardware that causes BPDUs not to arrive from the root switch on the port that a switch considers its root port

In the example, Switch A experiences a link fault. It is no longer receiving BPDUs over the link to the root switch.