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[All About Switches] Services Are Interrupted After a Switch Is Upgraded From V100R002 to V200R010

Latest reply: Mar 12, 2018 06:52:18 1441 1 0 0 0

Involved Products and Versions

All products and versions


As shown in Figure 1-1, SwitchA communicates with SwitchB through an intermediate transmission device.

Figure 1-1 Networking of service interruption after a switch is upgraded from V100R002 to V200R010



Fault Symptom

After SwitchA is upgraded from V100R002 to V200R010, it cannot communicate with SwitchB.

Cause Analysis

SwitchA sends BPDU packets from the designated interface GE/1/0/1 to GE/1/0/1 of SwicthB. Because the intermediate transmission device is faulty, SwicthB cannot receive BPDU packets from SwitchA, while GE/1/0/1 of SwicthA can receive BPDU packets sent from SwitchB. The priority of GE/1/0/1 on SwitchB is lower than that of GE/1/0/1 on SwitchA, so the interface status of SwitchA changes from FORWARDING to DISCARDING, resulting in the communication failure between SwitchA and SwitchB.

Troubleshooting Procedure

                          Step 1     After the upgrade, run the display stp brief command on SwitchA to view the status of the spanning tree, and find that GE1/0/1 is the designated interface and the interface status is DISCARDING (which should be FORWARDING in normal state).

<SwitchA> display stp brief
 MSTID   Port                        Role  STP State     Protection 
    0    GigabitEthernet1/0/1        DESI  DISCARDING    NONE

                          Step 2     Check the network planning and find out the reason why the interface receives packets with a lower priority. If the fault cannot be located, contact Huawei technical support.


Conclusions and Suggestions

Switches of different versions comply with different standards to process STP packets with a low priority. Modular switches running V100R002 and earlier versions, and fixed switches running versions earlier than V100R005 comply with 802.1s-2002 and earlier standards. Modular switches running versions later than V100R002, and fixed switches running V100R005 and later versions comply with 802.1D-2004 and 802.1Q-2005 standards.

The 802.1Q-2005 standard adds the status of INFERIOR_DESIGNATED for the interface status machine. If the interface role in BPDU packets received by the designated interface is the designated interface of another switch with a lower priority, and the interface status is LEARNING or FORWARDING, the interface status changes to DISCARDING.

1.       Modular switches running V100R002 and earlier versions, and fixed switches running versions earlier than V100R005 do not process received STP packets with low priority. After receiving STP packets, interfaces on modular switches running versions later than V100R002, and fixed switches running V100R005 and later versions will be blocked.

2.       Switches running versions earlier than V200R005 cannot process STP packets with double VLAN tags, while switches running V200R005 and later versions can process those packets.

Changes in the above two conditions may result in inconsistent STP status after the switch is upgraded. The change in condition 1 can be pre-determined by running the display stp command to check whether the designated interface receives STP packets. The change in condition 2 can be pre-determined only by analyzing whether packets contain double VLAN tags.

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Created Mar 12, 2018 06:52:18

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