Technical data

Using the BayStack 350 Series 10/100 Autosense Switch
1-40
893-00992-D
Spanning Tree Considerations
The spanning tree Path Cost parameter is recalculated based on the aggregate
bandwidth of the trunk. For example, Figure 1-26
shows a four port inter-switch
trunk (I1) with two port members operating at 100 Mb/s and the other two port
members operating at 10 Mb/s. Trunk I1 provides an aggregate bandwidth of 220
Mb/s. The Path Cost for I1 is 4 (Path Cost = 1000/LAN speed, in Mb/s). If a
second three port trunk (I2) is configured with an aggregate bandwidth of
210 Mb/s, with a comparable Path Cost of 4, the switch software chooses the
trunk with the larger bandwidth (I1) to determine the most efficient path.
Figure 1-26. Path cost arbitration example
The trunk is also viewed by management stations as a single spanning tree port.
The spanning tree port is represented by the trunk member with the lowest port
number. For example, if ports 13, 14, 15, and 16 are trunk members of Trunk I1,
the management station views Trunk I1 as spanning tree port 13.
BS0023A
1234562625
Activity
F Dx
10
100
789101112
13 14 15 16 17 18
Activity
F Dx
10
100
19 20 21 22 23 24
SW2
1234562625
Activity
F Dx
10
100
789101112
13 14 15 16 17 18
Activity
F Dx
10
100
19 20 21 22 23 24
SW1
I1 I2
100 Mb/s
100 Mb/s
10 Mb/s
100 Mb/s
100 Mb/s
10 Mb/s
10 Mb/s
Path Cost I1 = 4
Path Cost I2 = 4
Aggregate Bandwidth
220 Mb/s
Aggregate Bandwidth
210 Mb/s
350F-HD
10/100 Autosense Switch
350F-HD
10/100 Autosense Switch