3Com 10014299 manual Configure the interval for sending BPDUs

		Configure Bridge’s Routing Function 301
Table 330 Configure the interval for sending BPDUs
	Operation		Command
	Configure Hello Time timer		bridge stp timer hello seconds
	Restore the default value of the Hello Time timer		undo bridge stp timer hello

By default, the value of Hello Time timer is 2 seconds. It is in the range of 1 to 10 seconds.

When configuring the Hello Time timer, it should be noted that:

■In the spanning tree, all the bridges use the time value of Hello Time timer of the root bridge, and their own configurations take no effect.

■Too long a Hello Time will cause the bridge to recompute the spanning tree because it considers the packet dropping of the link as link fault, whereas too short a Hello Time will cause it to send BPDUs frequently and thus exacerbate the bridge CPU load. It is recommended that users use the default value.

fConfigure the forward delay for the port status transition

Link faults may cause the network to recompute the spanning tree topology. However, the recomputed new BPDU cannot be propagated throughout the network right away. If the newly elected root port and the designated port begin to forward data immediately, a temporary loop may be incurred. In STP, a transitional state mechanism is thus adopted. Specifically, the root port and the designated ports will undergo a transitional state for an interval of forward delay to enter the forwarding state to resume the data forwarding. Such a delay ensures that the new BPDU has already been propagated throughout the network before the data frames are forwarded according to the latest topology. The forward delay timer is thus used to control the interval for the system waiting to enter the Forwarding state.

Perform the following configuration in system view.

Table 331 Configure the forward delay for the port status transition

Operation	Command
Configure the forward delay timer	bridge stp timer
	forward-delay seconds
Restore the default value of the forward delay timer	undo bridge stp timer
	forward-delay

By default, the value of the forward delay timer is 15 seconds. It is in the range of 4 to 200 seconds.

When configuring the forward delay timer, note that:

■No matter what its individual configuration might be, all the bridges in the spanning tree should use the time value of the forward delay timer of the root bridge.

■If the forward delay is configured too short, temporary redundant paths may be introduced. If the forward delay is configured too long, however, the restoring of network connection may take a long time because the STP cannot converge to a stable state for a long period. It is recommended that users use the default value.

gConfigure the Max Age of BPDU