1-31When calculating the path cost of an aggregated link, the 802.1D-1998 standard does not take thenumber of the ports on the aggregated link into account, whereas the 802.1T standard does. Thefollowing formula is used to calculate the path cost of an aggregated link:Path cost = 200,000,000 / link transmission rateWhere, “link transmission rate” is the sum of the rates of all the unblocked ports on the aggregated linkmeasured in 100 Kbps.Configure the path cost for specific portsFollow these steps to configure the path cost for specified ports in system view:To do... Use the command... RemarksEnter system view system-view —Configure the path cost forspecified portsstp interface interface-list[ instance instance-id ] costcostRequiredAn MSTP-enabled switch cancalculate path costs for all itsports automatically.Follow these steps to configure the path cost for a port in Ethernet port view:To do... Use the command... RemarksEnter system view system-view —Enter Ethernet port view interface interface-typeinterface-number —Configure the path cost for theportstp [ instance instance-id ]cost costRequiredAn MSTP-enabled switch cancalculate path costs for all itsports automatically.Changing the path cost of a port may change the role of the port and put it in state transition. Executingthe stp cost command with the instance-id argument being 0 sets the path cost on the CIST for the port.Configuration example (A)# Configure the path cost of Ethernet 1/0/1 in MSTI 1 to be 2,000.1) Perform this configuration in system view system-view[Sysname] stp interface Ethernet 1/0/1 instance 1 cost 20002) Perform this configuration in Ethernet port view system-view[Sysname] interface Ethernet 1/0/1[Sysname-Ethernet1/0/1] stp instance 1 cost 2000Configuration example (B)# Configure the path cost of Ethernet 1/0/1 in MSTI 1 to be calculated by the MSTP-enabled switchaccording to the IEEE 802.1D-1998 standard.1) Perform this configuration in system view system-view
