HP VPN Firewall Appliances Network Management Configuration Guide
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transit to the forwarding state, resulting in loops in the switched network. The loop guard function can
suppress the occurrence of such loops.
The initial state of a loop guard-enabled port is discarding in every MSTI. When the port receives BPDUs,
it transits its state correctly. Otherwise, it stays in the discarding state to prevent temporary loops.
To enable loop guard, you must follow these guidelines:
• Configure loop guard on the root port and alternate ports of a device.
• 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.
To enable loop guard:
Ste
p
Command
Remarks
1. Enter system view.
system-view N/A
2. Enter Ethernet interface view or Layer 2
aggregate interface view.
interface interface-type
interface-number
N/A
3. Enable the loop guard function for the
ports.
stp loop-protection
By default, loop guard is
disabled.
Enabling TC-BPDU guard
When a device receives topology change (TC) BPDUs (the BPDUs that notify devices of topology
changes), the device flushes the forwarding address entries. If someone forges TC-BPDUs to attack the
device, the device will receive a large number of TC-BPDUs within a short time and be busy with flushing
forwarding address entries. 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.
HP recommend not disabling this feature.
To enable TC-BPDU guard:
Ste
p
Command
Remarks
1. Enter system view.
system-view N/A
2. Enable the TC-BPDU guard function.
stp tc-protection enable
Optional.
By default, TC-BPDU guard is
enabled.
3. Configure the maximum number of
forwarding address entry flushes that the
device can perform every 10 seconds.
stp tc-protection
threshold number
Optional.
The default setting is 6.