ZyXEL Communications MetroGigabit MGS3750-28F User Manual page 30

Chapter 6 Advanced Application Configurations
Figure 21 Com pat ible/ Rapid Spanning Tree Screen
The following t able describes t he fields in t his screen.
Table 14 Com pat ible/ Rapid Spanning Tree Screen
LABEL DESCRIPTION
St at us Click St at us t o go back t o t he Spa n n in g Tr e e Pr ot ocol St a t u s screen.
Bridge Priorit y Bridge priorit y is used in det erm ining t he root swit ch, root port and designat ed port .
The swit ch wit h t he highest priorit y ( lowest num eric value) becom es t he STP root
swit ch. I f all swit ches have t he sam e priorit y, t he swit ch wit h t he lowest MAC address
will t hen becom e t he root swit ch. Select a value from t he drop- down list box.
The lower t he num eric value you assign, t he higher t he priorit y for t his bridge.
Bridge Priorit y det erm ines t he root bridge, which in t urn det erm ines Hello Tim e, Max
Age and Forwarding Delay.
Hello Tim e This is t he t im e int erval in seconds bet ween BPDU ( Bridge Prot ocol Dat a Unit s)
configurat ion m essage generat ions by t he root swit ch. The allowed range is 1 t o 10
seconds.
Max Age This is t he m axim um t im e ( in seconds) t he Swit ch can wait wit hout receiving a BPDU
before at t em pt ing t o reconfigure. All Swit ch port s ( except for designat ed port s) should
receive BPDUs at regular int ervals. Any port t hat ages out STP inform at ion ( provided
in t he last BPDU) becom es t he designat ed port for t he at t ached LAN. I f it is a root
port , a new root port is select ed from am ong t he Swit ch port s at t ached t o t he
net work. The allowed range is 6 t o 40 seconds.
Forwarding Delay This is t he m axim um t im e ( in seconds) t he Swit ch will wait before changing st at es.
This delay is required because every swit ch m ust receive inform at ion about t opology
changes before it st art s t o forward fram es. I n addit ion, each port needs t im e t o list en
for conflict ing inform at ion t hat would m ake it ret urn t o a blocking st at e; ot herwise,
t em porary dat a loops m ight result . The allowed range is 4 t o 30 seconds.
As a general rule:
Note: 2 * (Forward Delay - 1) >= Max Age >= 2 * (Hello Time + 1)
MGS3750-28F User's Guide
30