Luxul XMS-1024P - Manual (Page 96)

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XMS-1024P
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LUX-UG-XMS-1024P Vers: 081314
MSTP
MSTP divides a Network into several MST Regions. The CST will encompass all MST
Regions in the Network, and multiple Spanning Trees can be generated in each MST
region. Each Spanning Tree is called an Instance. Like STP MSTP uses BPDUs to generate
the Spanning Tree topology. The only difference is that the BPDU for MSTP carries the
MSTP configuration information.
Port States
In an MSTP, Ports can have one of the following four states:
„
Forwarding: The Port can receive/forward Data, receive/send BPDU packets and learn
MAC Addresses.
„
Learning: In this status the Port can receive/send BPDU packets and learn
MAC addresses.
„
Blocking: In this status the Port can only receive BPDU packets and will drop all other
traffic received.
„
Disconnected: In this status the Port is not participating in STP.
Port Roles
In MSTP the following six roles exist:
„
Root Port: Indicates the Port that has the lowest path cost from this Bridge to the
Root Bridge and forwards packets to the root.
„
Designated Port: Indicates the Port that forwards packets to a downstream Network
segment or Switch.
„
Master Port: Indicates the Port that connects a MST region to the Common Root. The
path from the Master Port to the Common Root is the shortest path between this
MST Region and the Common Root.
„
Alternate Port: The Port can become a backup Port of a Root or Master Port.
„
Backup Port: The Port that is the backup Port of a Designated Port.
„
Disabled: The Port is not participating in the STP.
The following diagram shows the different Port roles.