3Com S7906E - Switch, Configuration Manual

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Enabling TC-BPDU guard
When receiving topology change (TC) BPDUs (the BPDUs used to notify topology changes), a switch
flushes its forwarding address entries. If someone forges TC-BPDUs to attack the switch, the switch will
receive a large number of TC-BPDUs within a short time and be busy with forwarding address entry
flushing. This affects network stability.
With the TC-BPDU guard function, you can set the maximum number of immediate forwarding address
entry flushes that the switch can perform within a certain period of time after receiving the first TC-BPDU.
For TC-BPDUs received in excess of the limit, the switch performs forwarding address entry flush only
when the time period expires. This prevents frequent flushing of forwarding address entries.
Follow these steps to enable TC-BPDU guard:
To do... Use the command... Remarks
Enter system view
system-view
—
Enable the TC-BPDU guard
function
stp tc-protection enable
Optional
Enabled by default
Configure the maximum
number of forwarding address
entry flushes that the device
can perform within a specific
time period after it receives the
first TC-BPDU
stp tc-protection threshold
number
Optional
6 by default
We recommend that you keep this feature enabled.
Remotely Configuring MSTP for an ONU
An S7900E switch installed with an OLT card can work as an EPON OLT. In this case, you can remotely
configure MSTP for an ONU attached to the OLT in ONU port view, as shown in the table below.
Note that:
z
An ONU port supports STP/RSTP/MSTP. However, an ONU port supports only MSTI 0 among all
MSTIs.
z
The STP priority of an ONU port is fixed to 0. To ensure the network operates normally, do not
configure the ONU as the STP root bridge.