User Manual

Moxa’s Managed Switch Next Generation OS (v3.x) User Manual
102
Click APPLY to finish.
BPDU Overview
BDPUs (Bridge Protocol Data Units) are the network communication frames used in the STP (Spanning Tree
Protocol). When two switches exchange messages, BDPUs are used to calculate the STP topology, and
determine the network communication route. A BDPU filter is often used to screen sending or receiving
BPDUs on a specific port of the switch.
BPDU Guard
BDPU Guard is a protection mechanism that prevents a port from receiving BPDUs. When an RSTP-enabled
port receives BPDUs, it will automatically be in the error-disable state, which means the port will in turn
switch to Block state. When STP is enabled, all ports are involved in the STP domain, sending and receiving
BPDUs. However, when BPDU Guard is enabled, all ports will not receive or send any BPDUs, as all
computers and unmanaged switches do not support STP. When BPDU Guard is enabled, all communications
will be treated as error-disabled, and the related ports will be blocked, therefore no more data will be sent
or received, protecting the network from a loop chain.
Root Guard
Root Guard prevents a designated port role from changing to root port role on reception of superior
information.
Loop Guard
Loop Guard prevents temporary loops in a network caused by non-designated ports changing to the
spanning-tree forwarding state due to a link failure in the topology.
BPDU Filter
BPDU Filter prevents a port from sending and processing BPDUs. A BPDU filter enabled port cannot
transmit any BPDUs and drop all received BPDU either.
Configuring BPDU Filter, BPDU/Root/Loop Guard Settings
First click Spanning Tree on the menu and then select the Guard tab. Next, click the edit icon on the port
you want to configure.