Interconnect Switch User Guide

Spanning Tree Protocol
D-12 Compaq ProLiant BL p-Class GbE Interconnect Switch User Guide
COMPAQ CONFIDENTIAL Codename: Vanilla Part Number: 263680-001 Last Saved On: 4/23/02 10:15 AM
Avoiding Trouble
Following are some tips for avoiding STP network problems.
Know Where the Root Is Located
Although the STP can elect a root bridge, a well-designed network will have an identifiable
root for each VLAN. Careful setup of the STP parameters will lead to the selection of the
preferred interconnect switch as the root for each VLAN. Redundant links can then be built
into the network. STP is well suited to maintaining connectivity in the event of a device
failure or removal, but is poorly suited to designing networks.
Know Which Links Are Redundant
Organize the redundant links and tune the port cost parameter of STP to force those ports to
be in the blocking state.
For each VLAN, know which ports should be blocked in a stable network. A network
diagram that shows each physical loop in the network and which ports break which loops is
extremely helpful.
Minimize the Number of Ports in the Blocking State
A single blocking port transitioning to the forwarding state at an inappropriate time can cause
a large part of a network to fail. Limiting the number of blocked ports helps to minimize the
risk of an inappropriate transition.