ZyXEL Communications GS1920-48HPv2, Руководство пользователя

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Chapter 13 Spanning Tree Protocol
GS1920v2 Series User’s Guide
137
STP Po rt Sta te s
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.
Fig ure 105
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:
• One Common and Internal Spanning Tree (CIST) that represents the entire network’s connectivity.
• Grouping of multiple bridges (or switching devices) into regions that appear as one single bridge on
the network.
• A VLAN can be mapped to a specific Multiple Spanning Tree Instance (MSTI). MSTI allows multiple
VLANs to use the same spanning tree.
Table 49 STP Port States
PO RT STATE DESC RIPTIO N
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.