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Type B and dual parenting to two switches cause MAC drift

Publication Date:  2018-02-28 Views:  505 Downloads:  0

Issue Description

New project deliver with type B and dual parenting to switches stack, when switch over OLT from active to standby, service will not be up.


Alarm Information

MAC address duplicate in network side and user side

Handling Process

1: Before switching to standby OLT, check terminal mac-address is learned in user side of active OLT, but also in network side of standby OLT.

2: This mean MAC address has already drifter to other OLT's NNI side. Will cause potential risk.

3: When Switching OLT from active to standby, terminal connected with standby OLT, MAC address is learned in UNI side of it. Still appear in the NNI side of this OLT at the same time

4: MAC address duplicate alarm reported to current OLT.

5: There will be two solution to fix this issue.

Root Cause

1:MAC address duplicate.

2: Default priority of NNI mac address learning is 3, UNI is 0, if same mac is learned at two sides, OLT will forward packets to NNI even if terminal has already connected to UNI side of OLT



1: Set mac address time to 10s, then mac learned in NNI of OLT will be eliminated and only left in UNI side

2: Set default priority of NNI mac address learning to 0, set default priority of UNI mac address learning also to 0, every time switch to standby OLT, it can forward packet to UNI side(new mac learned) when there are mac address in both UNI and NNI side.


For TYPE B dual parenting to two switches scenario, we'd better modify default priority of NNI and UNI mac address learning to same priority