ZyXEL Communications ZyWALL5UTM 4.0 User Manual

ZyWALL 5/35/70 Series User’s Guide

Chapter 6 Bridge Screens

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Once a stable network topology has been established, all bridges listen for Hello BPDUs 
(Bridge Protocol Data Units) transmitted from the root bridge. If a bridge does not get a Hello 
BPDU after a predefined interval (Max Age), the bridge assumes that the link to the root 
bridge is down. This bridge then initiates negotiations with other bridges to reconfigure the 
network to re-establish a valid network topology.

STP assigns five port states (see next table) to eliminate packet looping. A bridge port is not 
allowed to go directly from blocking state to forwarding state so as to eliminate transient 
loops.

Table 27   STP Port States

Disabled

STP is disabled (default).

Blocking

Only configuration and management BPDUs are received and processed.

Listening

All BPDUs are received and processed.

Learning

All BPDUs are received and processed. Information frames are submitted to the 

learning process but not forwarded.

Forwarding

All BPDUs are received and processed. All information frames are received and 

forwarded.

Select Bridge and click Apply in the MAINTENANCE Device Mode screen to have the 
ZyWALL function as a bridge. 

Click NETWORK, BRIDGE to display the screen shown next. Use this screen to configure 
bridge and RSTP (Rapid Spanning Tree Protocol) settings.