Enabling Loop Guard; Enabling Tc-Bpdu Guard - HP 3100 Series Configuration Manual

NOTE:
You cannot configure root guard and loop guard on a port at the same time.

Enabling loop guard

A device that keeps receiving BPDUs from the upstream device can maintain the state of the root
port and blocked ports. However, link congestion or unidirectional link failures might cause these
ports to fail to receive BPDUs from the upstream devices. The device will reselect the port roles:
Those ports in forwarding state that failed to receive upstream BPDUs will become designated ports,
and the blocked ports will transition 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, its state transitions normally. Otherwise, it stays in the discarding state to prevent temporary
loops.
Configure loop guard on the root port and alternate ports of a device.
To enable loop guard:
Step
Enter system view.
1.
Enter interface view or port
2.
group view.
Enable the loop guard
3.
function for the ports.
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.
To enable TC-BPDU guard:
Command
system-view
•
Enter Layer 2 Ethernet interface
view or Layer 2 aggregate
interface view:
interface interface-type
interface-number
•
Enter port group view:
port-group manual
port-group-name
stp loop-protection
87
Remarks
N/A
Use either command.
Disabled by default.