3Com Switch 7750 SeriesCommand Reference Guide – MSTP Chapter 1 MSTP Configuration Commands1-34Normally, when a port operates in full-duplex mode, the corresponding path cost isslightly less than that when the port operates in half-duplex mode.When calculating the path cost of an aggregated link, the 802.1D-1998 standard doesnot take the number of the ports on the aggregated link into account, whereas the802.1T standard does. The following formula is used to calculate the path cost of anaggregated link:Path cost = 200,000 / link transmission speed,Where the link transmission speed is the sum of the speeds of the unblocked ports onthe aggregated link, which is measured in 100 Kbps.Example# Configure to use the IEEE 802.1D-1998 standard to calculate the default path costsof ports.<3Com> system-viewSystem View: return to User View with Ctrl+Z.[3Com] stp pathcost-standard dot1d-1998# Configure to use the IEEE 802.1t standard to calculate the default path costs of ports.<3Com> system-viewSystem View: return to User View with Ctrl+Z.[3Com] stp pathcost-standard dot1t1.1.32 stp point-to-pointSyntaxstp point-to-point { force-true | force-false | auto }undo stp point-to-pointViewEthernet port viewParameterforce-true: Specifies that the link connected to the current Ethernet port is apoint-to-point link.force-false: Specifies that the link connected to the current Ethernet port is not apoint-to-point link.auto: Specifies to automatically determine whether or not the link connected to thecurrent Ethernet port is a point-to-point link.
