Nortel BayStack 380, Using Manual, Page: 87 / 218

Chapter 2 Network configuration 87
Using the BayStack 380 10/100/1000 Switch
Spanning tree considerations for MultiLink Trunks
The spanning tree Path Cost parameter is recalculated based on the aggregate
bandwidth of the trunk. For example,
Figure 39 shows a four-port trunk (T1) with
two port members operating at an aggregate bandwidth of 2.2 Gb/s, with a
comparable Path Cost of 4. When the Path Cost calculations for both trunks are
equal, the software chooses the trunk with the larger aggregate bandwidth (T1) to
determine the most efficient path.
Figure 39 Path Cost arbitration example
10488EB
T1 T2
100 Mb/s
100 Mb/s
1000 Mb/s
1000 Mb/s
Path Cost T1 = 1
S1
S2
Path Cost T2 = 5
Aggregate Bandwidth
2 Gb/s
Aggregate Bandwidth
200 Mb/s
BayStack
380
BayStack
380