Hello,
Today, I would like to share with you this topic which describes how to solve the Ring Network Caused by Two Online Ports in a Protection Group in Time delay OLT Ethernet Access Mode.
Devices Involved: MA5603T/ MA5680T/ MA5608T/ MA5683T/ MA5600T
Keywords:
timedelay, protection group, management interruption, ring network
Summary:
In normal cases, only one port in a protection group in timedelay mode is online. There is a low probability that a port fails to be disabled. As a result, two ports in the protection group are online at the same time, which causes a ring network on the network side, OLT management interruption, and services failures.
[Problem Description]
Trigger conditions:
Condition 1: A protection group for Ethernet access is configured to work in timedelay mode.
Condition 2: There is a low probability that this problem occurs in either of the following scenarios:
Scenario 1: The system is reset (on the CLI, power-off, or upgrade).
Scenario 2: Two ports in a protection group are on the same board, and the board is reset.
Note: The board where the Ethernet ports of a protection group reside does not distinguish the type and slot, and the ports do not distinguish the type and position.
Symptom:
After the OLT is restarted, the two ports in a protection group in timedelay mode are online, and a ring network is generated on the network side. As a result, the OLT management is interrupted and services are unavailable. (A timedelay protection group is different from an aggregation group. When two ports are online, the unknown unicast, unknown multicast, or broadcast packets received by one port can be forwarded by the other port.)
Identification method:
Check whether Ethernet access is used, and whether the protection group works in timedelay mode.
Method 1: When the problem occurs, check whether the two ports on the local device are online.
Method 2: After the fault is rectified, run the display eth port debug info command to check whether two ports are online at the same time.
In the preceding example, ports 0/19/0 and 0/20/0 of the protection group are online in sequence.
Method 3: Before and after the problem occurs, check whether two ports on the peer device are online at the same time.
[Root Cause]
In a protection group in timedelay mode for Ethernet access, after the system or a board is reset and configurations are restored, there is a low probability that the system fails to disable a port in the configuring state. As a result, the two ports in the protection group are online at the same time.
[Impact and Risk]
1. A ring network is generated on the network side, and services on the OLT are unavailable.
2. If the OLT is managed in inband mode, the management is interrupted.
[Measures and Solutions]
Workaround
Measure 1: Before the system is upgraded or restarted, shut down a port on the peer device or remove the fiber from a port. After the system is restarted, run the undo shutdown command to enable the port or insert the fiber back.
Measure 2: Disable the protection group before upgrading or restarting the system. After the system is restarted, enable the protection group.
Note: The prerequisite for the preceding two measures is that the master port in the protection group must be online.
Recovery measure
Measure 1: Shut down a port on the peer device. After the system restarts, run the undo shutdown command to enable the port.
Measure 2: Remove and then insert the fiber of any port in the protection group.
Solution
In the Ethernet access scenario where a protection group in timedelay mode is configured, the system is optimized to ensure that a port in the configuring state can be disabled successfully.
This issue will be resolved in MA5600V800R017C10 SPH233 (to be released at the end of March 2020), MA5600V800R018C00 SPH210 (to be released at the end of April 2020), MA5600V800R018C10 SPH217 (to be released at the end of March 2020), and later versions.
[Precaution Expiration]
This precaution expires after device versions are upgraded to the specified patched versions.
Reference:
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