EtherWAN EX24000, User Manual

Page: 108 / 239

Configuring the CST Network Diameter
When using MSTP, the Max Age parameter is used for the CST (Common Spanning Tree)
topology simply as a hop count limit on how far the Spanning Tree protocol packet can
propagate throughout the CST topology, therefore, the Max Age must be configured with a
value that is greater than the network diameter of the CST topology. The Max Age
parameter will need to be configured correctly on both the CIST Root Bridge as well as on
the Backup CIST Root Bridge (in the event when the CIST Root Bridge fails).
Setting the MAX Age, Forward Delay and Hello Timer
Navigate to the STP/Ring Global Configuration page:
1. Click on the + next to STP/Ring .
2. Click on Global Configuration .
Relationship between Max Age, Forward Delay and Hello Time
The following rules must be followed when setting the Max Age , Forward Delay and
Hello Timer :

Max Age >= 2 × (Hello Time + 1.0 second)

2 × (Forward Delay – 1.0 second) >= Max Age
To change the Max Age , Forward Delay and Hello Timer (see Figure 49 ):
1. Enter the Max Age in the text box to the right of Max Age (6..40 sec) label.
2. Enter the Hello Time in the text box to the right of the Hello Time (1..10 sec)
label.
3. Enter the Forward Delay in the text box to the right of the Forward Delay (4..30
sec) label.
4. Click on the Update Setting button.
5. Save the configuration (see the Save Configuration Page )
108
EX24000 Switch Users Guide