D-Link DES-3224 Spanning Tree Algorithm, Bridge Priority, Root Cost, Hello Time, Max Age Time

10/100 Auto Negotiation Switch User’s Guide

Spanning Tree Algorithm

Spanning Tree Algorithm can be enabled or disabled. Use Spanning Tree to prevent network loops.

Bridge Priority

The Bridge Priority can be from 0 to 65535. Zero is the highest Bridge Priority. The higher the Bridge Priority the greater the chance that the DES-3224 will be selected as the Root Bridge. The DES-3224 with the highest Bridge Priority is the Root Bridge.

Root Cost

The Root Cost is the number of times a packet is regenerated before reaching its destination. A source sends a packet to the first device (switch or hub) on the network. When the packet reaches the next hub or switch and it is sent out again, the Path Cost becomes two. Each switch and active hub regenerates the packet. To determine the Root Path Cost, count the number of times the packet is regenerated.

The switch with the lowest Path Cost is the Root Bridge. Make the Root Bridge the best switch on the network.

Hello Time

Is the interval between two transmissions of packets sent by the Root Bridge to tell all other switches that it is the Root Bridge. The Hello Time can be set manually, with a range in seconds from 1 to 10. If the Hello Time is set for the switch and the switch is not the Root Bridge then the Hello Time will not take effect until the switch becomes the Root Bridge.

Forward Delay Time

This is the time any port on the DES-3224 spends in the listening state while moving from the listening state to the forwarding state. It can be set from 4 to 30 seconds.

Use the following formula when setting the Hello Time and the Forward Delay Time:

2 x (Forward Delay minus 1 second) > Max Age

2 x (Hello Time plus 1 second) < Max Age

Max Age Time

Is the time a non-root bridge waits for a packet to be sent. At the end of the Max Age, if a packet has not been received from the Root Bridge, the DES-3224 will start sending its own packets and request permission to become the Root Bridge. If it turns out that the DES-3224 has the lowest Bridge Identifier it will become the Root Bridge.

The switch with the lowest Bridge Identifier is the Root Bridge. It is best to make the Root Bridge the best switch on the network to ensure the best network performance and reliability.

Managing the DES-3224 41