Chapter 8 Configuring VLANs
Load Sharing Using STP
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Catalyst 2900 Series XL and Catalyst 3500 Series XL Software Configuration Guide
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Load Sharing Using STP Path Cost
You can configure parallel trunks to share VLAN traffic by setting different path
costs on a trunk and associating the path costs with different sets of VLANs. The
VLANs keep the traffic separate; because no loops exist, STP does not disable the
ports; and redundancy is maintained in the event of a lost link.
In
Figure 8-6
, trunk ports 1 and 2 are 100BASE-T ports. The path costs for the
VLANs are assigned as follows:
•
VLANs 2 through 4 are assigned a path cost of 30 on trunk port 1.
•
VLANs 8 through 10 retain the default 100BASE-T path cost on trunk port 1
of 19.
•
VLANs 8 through 10 are assigned a path cost of 30 on trunk port 2.
•
VLANs 2 through 4 retain the default 100BASE-T path cost on trunk port 2
of 19.
Figure 8-6
Load-Sharing Trunks with Traffic Distributed by Path Cost
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Switch 1
Switch 2
Trunk port 1
VLANs 2-4 (path cost 30)
VLANs 8-10 (path cost 19)
Trunk port 2
VLANs 8-10 (path cost 30)
VLANs 2-4 (path cost 19)