HP 6125G HP 6125G & 6125G/XG Blade Switches Layer 2 - LAN Switching Co - Page 83

Link speed 10 Gbps Port type Path cost IEEE 802.1d-1998 Aggregate interface containing 3 Selected ports Aggregate interface containing 4 Selected ports Single port Aggregate interface containing 2 Selected ports Aggregate interface 2 containing 3 Selected ports Aggregate interface containing 4 Selected ports IEEE 802.1t 6666 5000 2000 1000 666 500 Private standard 16 14 2 1 1 1 Configuration restrictions and guidelines • When it calculates path cost for an aggregate interface, IEEE 802.1t takes into account the number of Selected ports in its aggregation group, but IEEE 802.1d-1998 does not. The calculation formula of IEEE 802.1t is: Path cost = 200,000,000/link speed (in 100 kbps), where link speed is the sum of the link speed values of the Selected ports in the aggregation group. • When multiple ports operate at a rate higher than 10 Gbps and the standard for default path cost calculation is dot1d-1998 or legacy, the path cost of a single port or an aggregate interface takes the smallest value. As a result, the forwarding path selected might not be optimal. To solve this problem, use dot1t as the standard for default path cost calculation, or manually set the path cost for a port (Configuring path costs of ports). Configuration procedure To specify a standard for the device to use when it calculates the default path cost: Step 1. Enter system view. 2. Specify a standard for the device to use when it calculates the default path costs of its ports. Command system-view Remarks N/A stp pathcost-standard { dot1d-1998 | dot1t | legacy } Optional. legacy by default. Configuring path costs of ports When the path cost of a port changes, the system re-calculates the role of the port and initiates a state transition. To configure the path cost of ports: Step 1. Enter system view. Command system-view Remarks N/A 74