Run the display stp command to check statistics about the received TC packets and TCN packets.
<Huawei> display stp interface Eth2/0/1
----[CIST][Port2(Ethernet2/0/1)][FORWARDING]----
Port Protocol :Enabled
Port Role :Designated Port
Port Priority :128
Port Cost(Dot1T ) :Config=auto / Active=199999
Designated Bridge/Port :4096.00e0-fc01-0005 / 128.2
Port Edged :Config=default / Active=disabled
Point-to-point :Config=auto / Active=true
Transit Limit :147 packets/hello-time
Protection Type :None
Port STP Mode :MSTP
Port Protocol Type :Config=auto / Active=dot1s
PortTimes :Hello 2s MaxAge 20s FwDly 15s RemHop 20
TC or TCN send :1
TC or TCN received :0
BPDU Sent :124008
TCN: 0, Config: 0, RST: 0, MST: 124008
BPDU Received :0
TCN: 0, Config: 0, RST: 0, MST: 0
l If a large number of TC packets and TCN packets are received, run the stp tc-protection
command in the system view to suppress TC-BPDUs. After this command is used, only three
TC packets are processed within a Hello interval by default. Run the stp tc-protection
threshold command to set the maximum number of TC packets that can be processed. To
change the hello interval, run the stp timer hello command.
[Huawei] stp tc-protection
[Huawei] stp tc-protection threshold 5
[Huawei] stp timer hello 200
l If a small number of TC packets are received, go to step 4.
Step 4 Check whether loops occur on the network.
When multiple interfaces of a device belong to the same VLAN, if a loop occurs between two
interfaces, packets are forwarded only between these interfaces in the VLAN. Consequently,
CPU usage of the device becomes high.
Run the display current-configuration command to check whether the device is enabled to
generate an alarm when MAC address flapping is detected.
#
loop-detect eth-loop alarm-only
#
l If this function is not configured, run the loop-detect eth-loop alarm-only command to
configure this function. If a loop occurs on the network, an alarm is generated when two
interfaces of the device learn the same MAC address entry. For example:
Feb 22 2011 18:42:50 Huawei L2IFPPI/4/MAC_FLAPPING_ALARM:OID
1.3.6.1.4.1.2011.5.25.42.2.1.7.12The mac-address has flap value .
(L2IfPort=0,entPhysicalIndex=0, BaseTrapSeverity=4, BaseTrapProbableCause=549,
BaseTrapEventType=1, MacAdd=0000-c0a8-0101,vlanid=100,
FormerIfDescName=Ethernet1/0/0,CurrentIfDescName=Ethernet1/0/1,DeviceName=HUAWE
I)
Check the interface connection and networking information based on the alarm:
– If no ring network is required, shut down one of the two interfaces based on the networking
diagram.
– If the ring network is required, disable loop detection and enable loop prevention
protocols, such as STP.
l If the loop-detect eth-loop alarm-only command is used on the device but no alarm is
generated, go to step 5.
Huawei AR2200-S Series Enterprise Routers
Troubleshooting 2 System
Issue 01 (2012-01-06) Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
9
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