Chapter 13 Spanning Tree Protocol
GS1920 Series User’s Guide
121
STP Port States
STP assigns five port states 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.
Multiple RSTP
MRSTP (Multiple RSTP) is ZyXEL’s proprietary feature that is compatible with RSTP and STP. With
MRSTP, you can have more than one spanning tree on your Switch and assign port(s) to each tree.
Each spanning tree operates independently with its own bridge information.
In the following example, there are two RSTP instances (MRSTP 1 and MRSTP2) on switch A.
To set up MRSTP, activate MRSTP on the Switch and specify which port(s) belong to which spanning
tree.
Note: Each port can belong to one STP tree only.
Figure 90 MRSTP Network Example
Multiple STP
Multiple Spanning Tree Protocol (IEEE 802.1s) is backward compatible with STP/RSTP and
addresses the limitations of existing spanning tree protocols (STP and RSTP) in networks to include
the following features:
Table 46 STP Port States
PORT STATE DESCRIPTION
Disabled STP is disabled (default).
Blocking Only configuration and management BPDUs are received and processed.
Listening All BPDUs are received and processed.
Note: The listening state does not exist in RSTP.
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.
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