4-21z Based on the network diameter you configured, MSTP automatically sets an optimal hello time,forward delay, and max age for the device.z The configured network diameter is effective for the CIST only, and not for MSTIs. Each MSTregion is considered as a device.z The network diameter must be configured on the root bridge. Otherwise, it will not take effect.Configuring Timers of MSTPMSTP involves three timers: forward delay, hello time and max age. You can configure these threeparameters for MSTP to calculate spanning trees.z To prevent temporary loops on a network, MSTP sets an intermediate port state called learningbetween the discarding state and the forwarding state, that is, before a port in the discarding statecan transit to the forwarding state, it needs to go through the learning state. Forward delay is thedelay time for port state transition. This is to ensure that the state transition of the local port andthat of the peer occur in a synchronized manner.z Hello time is the time interval at which a device sends configuration BPDUs to the surroundingdevices to ensure that the paths are fault-free. If a device fails to receive configuration BPDUswithin a certain period of time, it starts a new spanning tree calculation process.z MSTP can detect link failures and automatically restore blocked redundant links to the forwardingstate. A device on the CIST determines whether a configuration BPDU received by a port hasexpired according to the max age parameter. If yes, it starts a new spanning tree calculationprocess. The max age set for an MSTI does not take effect.These three timers set on the root bridge of the CIST apply on all the devices on the entire switchednetwork.Make this configuration on the root bridge only.Follow these steps to configure the timers of MSTP:To do... Use the command... RemarksEnter system view system-view —Configure the forward delaytimer stp timer forward-delay timeOptional1,500 centiseconds (15seconds) by defaultConfigure the hello timer stp timer hello timeOptional200 centiseconds (2 seconds)by default
