Network Load Sharing Using Stp Path Cost; Feature Interactions - Cisco Catalyst 2960 series Configuration Manual

Configuring VLAN Trunks

Network 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, blocking different ports for different VLANs. The VLANs keep
the traffic separate and maintain redundancy in the event of a lost link.
Trunk ports 1 and 2 are configured as 100BASE-T ports. These VLAN path costs are assigned:
• 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 5: Load-Sharing Trunks with Traffic Distributed by Path Cost
Related Topics
Configuring Load Sharing Using STP Path Cost, on page 75

Feature Interactions

Trunking interacts with other features in these ways:
• A trunk port cannot be a secure port.
• Trunk ports can be grouped into EtherChannel port groups, but all trunks in the group must have the
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same configuration. When a group is first created, all ports follow the parameters set for the first port
to be added to the group. If you change the configuration of one of these parameters, the switch propagates
the setting that you entered to all ports in the group:
◦ Allowed-VLAN list.
◦ STP port priority for each VLAN.
◦ STP Port Fast setting.
◦ Trunk status:
If one port in a port group ceases to be a trunk, all ports cease to be trunks.
Catalyst 2960-X Switch VLAN Configuration Guide, Cisco IOS Release 15.0(2)EX
Feature Interactions
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