R2511-HP MSR Router Series Layer 2 - LAN Switching Configuration Guide(V5)

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• legacy—The device calculates default path costs for ports based on a private standard.
Table 10 sho
ws a comparison between link speeds and path costs for each of these standards.
Table 10 Mappings between the link speed and the path cost
Link speed Port type
Path cost
IEEE
802.1d-1998
IEEE 802.1t Private standard
0 N/A 65535 200,000,000 200,000
10 Mbps
Single port
100
2,000,000 2000
Aggregate interface
containing 2 Selected ports
1,000,000 1800
Aggregate interface
containing 3 Selected ports
666,666 1600
Aggregate interface
containing 4 Selected ports
500,000 1400
100 Mbps
Single port
19
200,000 200
Aggregate interface
containing 2 Selected ports
100,000 180
Aggregate interface
containing 3 Selected ports
66,666 160
Aggregate interface
containing 4 Selected ports
50,000 140
1000 Mbps
Single port
4
20,000 20
Aggregate interface
containing 2 Selected ports
10,000 18
Aggregate interface
containing 3 Selected ports
6666 16
Aggregate interface
containing 4 Selected ports
5000 14
10 Gbps
Single port
2
2000 2
Aggregate interface
containing 2 Selected ports
1000 1
Aggregate interface
containing 3 Selected ports
666 1
Aggregate interface
containing 4 Selected ports
500 1
Configuration 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 the link speed of a single port exceeds 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