1-37
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System view
Parameters
dot1d-1998
: Uses the IEEE 802.1D-1998 standard to calculate the default path costs of ports.
dot1t
: Uses the IEEE 802.1t standard to calculate the default path costs of ports.
legacy
: Uses the proprietary standard to calculate the default path costs of ports.
Description
Use the
stp pathcost-standard
command to set the standard to be used to calculate the default path
costs of the links connected to the switch.
Use the
undo stp pathcost-standard
command to specify to use the default standard.
By default, a switch uses the legacy standard to calculate the default path costs of ports.
Table 1-8
Link speeds and the corresponding path costs
Link speed
Operating mode
(half-/full-duplex)
802.1D-1998
IEEE 802.1t
Proprietary
standard
0 —
65,535
200,000,000
200,000
10 Mbps
Half-duplex/Full-duplex
Aggregated link 2 ports
Aggregated link 3 ports
Aggregated link 4 ports
100
95
95
95
200,000
1,000,000
666,666
500,000
2,000
1,800
1,600
1,400
100 Mbps
Half-duplex/Full-duplex
Aggregated link 2 ports
Aggregated link 3 ports
Aggregated link 4 ports
19
15
15
15
200,000
100,000
66,666
50,000
200
180
160
140
1,000 Mbps
Full-duplex
Aggregated link 2 ports
Aggregated link 3 ports
Aggregated link 4 ports
4
3
3
3
200,000
10,000
6,666
5,000
20
18
16
14
10 Gbps
Full-duplex
Aggregated link 2 ports
Aggregated link 3 ports
Aggregated link 4 ports
2
1
1
1
200,000
1,000
666
500
2
1
1
1
Normally, when a port operates in full-duplex mode, the corresponding path cost is slightly less than that
when the port operates in half-duplex mode.
When the path cost of an aggregated link is calculated, the 802.1D-1998 standard does not take the
number of the ports on the aggregated link into account, whereas the 802.1T standard does. The
following formula is used to calculate the path cost of an aggregated link:
Path cost = 200,000 / link speed,
In this formula, the link speed is the sum of the speeds of the unblocked ports on the aggregated link,
which is measured in 100 Kbps.