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Cisco Bug: CSCta06502 - [39-CRS-FIT] mpls_ldp crash when feature unconfigured

Last Modified

May 16, 2018

Products (1)

  • Cisco Carrier Routing System

Known Affected Releases


Description (partial)


LDP crashes after LDP config was unconfigured, with NSR and GR enabled.


Crash occurs because LDP asserts when peer is release because it's on the NSR 
delay list.  Peer should be removed from list when peer goes down, so it 
shouldn't be on list when peer is released.   

The peer ended up on the list as a result of the following sequence of events:

1) NSR unconfig is applied. The global NSR config flag is cleared and async 
event is enqueued to process the unconfig event later.

2) GR unconfig is applied, resulting in sessions going down.  Since NSR 
config flag is already cleared, NSR processing is skipped and the peer NSR 
state doesn't transition to NONE state.

3) IPC disconnect is received from standby LDP resulting in peer 
transitioning to WAIT state and being added to NSR delay list.  NOTE: If peer 
NSR state was in NONE state when IPC disconnect was received, peer would have 
been skipped and would have not transitioned in WAIT state.

4) Peer is released and LDP asserted because NSR delay list was not empty.

NOTE:  LDP asserted before NSR async event was received and processed. If NSR 
async event would have been received before peer was released, obviously 
crash would not have happened.
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