Draytek VigorSwitch P1085, User Manual, Page: 57 / 267

VigorSwitch P1085 User’s Guide 49
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The Spanning Tree Protocol (STP) is a network protocol that ensures a loop-free topology for
any bridged Ethernet local area network.
Bridge Protocol Data Units (BPDUs) are frames that contain information about the Spanning
Tree Protocol (STP). Switches send BPDUs using a unique MAC address from its origin port and
a multicast address as destination MAC (01:80:C2:00:00:00, or 01:00:0C:CC:CC:CD for Per
VLAN Spanning Tree).
For STP algorithms to function, the switches need to share information about themselves and
their connections. What they share are bridge protocol data units (BPDUs).
BPDUs are sent out as multicast frames to which only other layer 2 switches or bridges are
listening. If any loops (multiple possible paths between switches) are found in the network
topology, the switches will co-operate to disable a port or ports to ensure that there are no
loops; that is, from one device to any other device in the layer 2 network, only one path can
be taken.
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This page allows a user to configure and display Spanning Tree Protocol (STP) property
configuration.
Available settings are explained as follows:
Item Description
STP Mode Set the operating mode of Spanning Tree (STP).

Disabled – Disable the STP operation.

STP - Enable the Spanning Tree (STP) operation.

RSTP - Enable the Rapid Spanning Tree (RSTP) operation.
BPDU Handling Specify the BPDU forward method when the STP is disabled.

Filtering - Filter the BPDU when STP is disabled.

Flooding - Flood the BPDU when STP is disabled.