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Cisco Bug: CSCtd80083 - RDI sent with CCMs after dynamically changing encap and tags

Last Modified

May 10, 2018

Products (1)

  • Cisco ASR 9000 Series Aggregation Services Routers

Known Affected Releases

3.9.1.BASE 4.0.0.BASE

Description (partial)

Symptom:

Following a specific sequence of configuration events in a set of nested domains (see conditions below).  It is possible to get into a state where CFM in the outermost domain is sending RDI when there is currently no remote defect in the network.

Conditions:

This issue can only occur with nested domains, and only following specific configuration changes on a MEP in the inner domain which would have caused CCMs from the inner domain to 'leak' to the outer domain.

An example scenario is as follows:

Four interfaces, connected as follows:

A --- B --- C --- D

A & B on the same router, A is configured with a level 5 UP MEP, B is configured with a level 3 DOWN MEP.

C & D on the same router, D is configured with a level 5 UP MEP, C is configured with a level 3 DOWN MEP.

The user has configured B & C with a QinQ encapsulation.

In order to trigger the error case, the user configures 'encapsulation default' on C.  This causes the MEP to be removed & CCMs from B to 'leak' to D.  D sees these CCMs, identifies a potential problem with intersecting domains &, as per the standard, sets RDI due to wrong level & wrong MAID.

When the user reconfigured the QinQ encapsulation, the RDI bit may not be cleared on D.
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