174 CHAPTER 10: RSTP CONFIGURATIONConfigure theBridgepreference of aSwitchThe Bridgepreference of aSwitch is 32768.A Switch can be made the root bridge byspecifying its Bridge preference to 0.Specify ForwardDelay, HelloTime, and MaxAgeForward Delay fixeson 15 seconds,Hello Times on 2seconds, and MaxAge on 20seconds.The other Switches copies theconfiguration on the root bridge withrespect to these time parameters. You cantherefore only configure them on the rootbridge. The default values are highlyrecommended.Specify themaximumtransmissionrate of STPpackets on aportNo Ethernet portcan send morethan 3 STP packetswithin one HelloTime.The more STP packets a port sends withinone Hello Time, the more resources areconsumed. It is therefore recommended tolimit the transmission rate of STP packetson a port, preferably to the default value.Configurewhether toconnect a portwith apeer-to-peer linkRSTP can detectautomaticallywhether thecurrent Ethernetport is connect to apeer-to-peer link.The two ports connected with apeer-to-peer link can rapidly transit to theforwarding status by sending synchronouspackets, eliminating unnecessaryforwarding delay.Specify the PathCost on a portSpecify thestandard tofollow in PathCost calculationThe Switch getsthe path cost of aport from the linkrate under the IEEE802.1t standard.The path cost of a port is closely related tothe transmission rate of the link the portconnected with. The larger the link rate is,the smaller the path cost shall be. It isrecommended to use the defaultconfiguration.Specify mCheckfor a port- You can change the operational mode ofa port from STP-compatible to RSTP.Configure theprotectionfunctions on aSwitchNo protectionfunction is enabledon a Switch.It is recommended to enable the Rootprotection function on the root bridge.Switch C &Switch DEnable the STPfeature on theSwitchEnable the STPfeature on theportThe STP feature isdisabled from theSwitch, but will beenabled on allports once beingenabled on theSwitch.The configuration of STP feature status onthe port will not take effect if the STPfeature is disabled from the Switch.Configure RSTPoperationalmodeThe Switch worksin RSTP mode.If there are Switches respectively runningSTP and RSTP on the network, it isrecommended to set the Switch inSTP-compatible mode.Configure theBridgepreference of aSwitchThe Bridgepreference of aSwitch is 32768.A Switch can be made the designatedbridge of the downstream Switches byspecifying an appropriate Bridgepreference in the STP calculation.Device Configuration Default Value Note
