3Com 10014298 manual Port, Configuring in system view, Configuring in Ethernet port view

196CHAPTER 8: STP OPERATION

that is too short, the switch frequently sends configuration BPDU, which adds burden and wastes the network resources.

A max age that is too short, can cause the network device to calculate the spanning tree frequently and mistake the congestion as a link fault. If the max age is too long, the network device may not be able to discover the link fault and recalculate the spanning tree in time, which weakens the auto-adaptation capacity of the network. The default value is recommended.

To avoid frequent network flapping, the values of hello time, forward delay and maximum age should guarantee the following formulas equal.

2 * (forward-delay - 1seconds) >= maximum-age

maximum-age >= 2 * (hello + 1.0 seconds)

You should use the stp root primary command to specify the network diameter and hello time of the switching network so MSTP will calculate automatically and give better values.

By default, forward delay is 15 seconds, hello time is 2 seconds, and max age is 20 seconds.

Configuring the Max The max transmission speed on a port specifies how many MSTP packets will be Transmission Speed on transmitted, every hello time, through the port.

a Port

The max transmission speed on a port is limited by the physical state of the port and the network structure. You can configure it according to the network conditions.

You can configure the max transmission speed on a port in the following ways.

Configuring in system view

Perform the following configuration in system view.

Table 198 Configure the Max Transmission Speed on a Port

Operation	Command
Configure the max transmission speed on a	stp interface interface-list
port.	transit-limit packetnum

Restore the max transmission speed on a port. undo stp interface interface-listtransit-limit

Configuring in Ethernet port view

Perform the following configuration in Ethernet port view.

Table 199 Configure the Max Transmission Speed on a Port

Operation	Command
Configure the max transmission speed on a	stp transit-limit packetnum
port.
Restore the max transmission speed on a port. undo stp		transit-limit

For more about the commands, see the Switch 7750 Command Reference Guide.