IBM 12.1(22)EA6 Configuring Spanning-Tree Features

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Cisco Systems IntelligentGigabit Ethernet Switch Modules for the IBM BladeCenter, Software Configuration Guide

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Chapter9 Configuring STP

Configuring Spanning-Tree Features

A port-blocking filter exists between the switch external ports and the switch internal management

module ports. This filter prevents operational traffic (such as unicast, multicast, and b roadcast traffic)

entering a switch external port from being forwarded to the management module, and from the

management module to the external ports.

However, STP does not recognize that this filter exists. During topology discovery, STP incorrectly

perceives that an external port is forwarding operational traffic to the internal management module po rts

and that a Layer 2 loop exists. STP changes the state of the internal management module port to blocked

state. This action is acceptable for operational traffic, but not for management (non-operational) traffic.

The default path cost value on the switch internal management module ports is 100. The intent is to block

operational traffic from being forwarded to the management module through any external port in the

non-management VLAN. STP will see the cost of the management module port as the most expensive

and block it. We do not recommend using the management module ports to carry operational traffic. This

does not apply to the management VLAN on the management module ports. The switch prevents STP

from blocking the management VLAN on the management module po rts. STP blocking of VLANs on

the management module ports is permitted for non-management VLANs only.

Configuring Spanning-Tree Features

These sections describe how to configure spanning-tree features:

•Default Spanning-Tree Configuration, page 9-12

•Spanning-Tree Configuration Guidelines, page 9-12

•Changing the Spanning-Tree Mode, page 9-13 (required)

•Disabling Spanning Tree, page 9-14 (optional)

•Configuring the Root Switch, page 9-15 (optional)

•Configuring a Secondary Root Switch, page 9-17 (optional)

•Configuring the Port Priority, page 9-17 (optional)

•Configuring the Path Cost, page 9-19 (optional)

•Configuring the Switch Priority of a VLAN, page 9-20 (optional)

•Configuring Spanning-Tree Timers, page 9-21 (optional)