forward-delay

Usage Guidelines

This command specifies how long the listening and learning states last before the interface begins the forwarding of all spanning-tree instances.

STP interface states:

• Listening - The interface processes the Bridge Protocol Data Units (BPDUs) and awaits possible new information that might cause it to return to the blocking state.
• Learning - The interface does not yet forward frames (packets), instead it learns source addresses from frames received and adds them to the filtering database (switching database).
• Forwarding - An interface receiving and sending data, normal operation. STP still monitors incoming BPDUs that can indicate it should return to the blocking state to prevent a loop.
• Blocking - An interface that can cause a switching loop, no user data is sent or received, but it might go to the forwarding state if the other links in use fail and the STP determines that the interface may transition to the forwarding state. BPDU data continues to be received in the blocking state.

When you change the spanning-tree forward-delay time, it affects all spanning-tree instances. When configuring the forward-delay, the following relationship should be kept:

(2 × (forward-delay - 1)) >= max-age >= (2 × (hello-time + 1))

Enter no forward-delay to return to the default settings.

The command is the same regardless of which type of STP is enabled.