H3C Technologies H3C S10500 Series Switches - Manual (Page 108)

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Configure loop guard on the root port and alternate ports of a device.
Follow these steps to enable loop guard:
To do... Use the command... Remarks
Enter system view system-view —
Enter Layer 2 Ethernet
interface view or Layer 2
aggregate interface view
interface interface-type
interface-number
Enter interface
view or port
group view
Enter port group view
port-group manual
port-group-name
Required
Use either command.
Enable the loop guard function for the ports stp loop-protection
Required
Disabled by default.
NOTE:
•
Do not enable loop guard on a port that connects user terminals. Otherwise, the port will stay in the
discarding state in all MSTIs because it cannot receive BPDUs.
• You cannot configure edge port settings and loop guard, or configure root guard and loop guard on a
port at the same time.
Enabling TC-BPDU guard
When a switch receives topology change (TC) BPDUs (the BPDUs that notify devices of topology
changes), the 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 device can perform every a specified period of time (10 seconds). For TC-BPDUs
received in excess of the limit, the device performs a forwarding address entry flush 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 every 10 seconds
stp tc-protection threshold
number Optional
6 by default.
NOTE:
H3C does not recommend you disable this feature.