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Cisco Bug: CSCvi22885 - 651 Scalability: mpls_ldp crash while adding mpls ldp cfg with CSI interface egress sdr

Last Modified

Oct 23, 2019

Products (1)

  • Cisco Network Convergence System 6000 Series Routers

Known Affected Releases


Description (partial)


MPLS LDP process could not send updates to MPLS_LSD process. this resulted an inconsistency in respective process database. Due to that traffic black hole can happen.

Through below procedure we can detect the issue.

1. ?show mpls ldp forwarding detail? can show the forwarding updates time with ?N/A?
2. In some cases, LDP crash can be seen as well.

Example of CLI output from show tech ldp information received from customer router :-
show mpls ldp ipv4 forwarding detail location 0/RP0/CPU0 
Prefix          Label   Label(s)       Outgoing     Next Hop            Flags
                In      Out            Interface                        G S R
--------------- ------- -------------- ------------ ------------------- -----    28478   29013          BE1         G    
                        [ table-id 0xe0000000, RIB flags 0x0000, load-metric 0,
                          path-id 1;
                          label from: peer ]
  RIB route: table-id 0xe0000000, version 17832, priority 7, metric 10030
             source 5, type 0x80, flags 0x0
    Routing   : Total 5169, Last at Jun 14 12:40:02.499 (02:36:01 ago)
    Forwarding: Total 2393, Last at N/A>>>>>>>>>>>>>> The N/A Output indicates that update to LSD was not forwarded.

A spike of route churns caused by interface flaps and other topology changes triggers many RIB updates to be sent to LDP process.
Overwhelmed by all those updates, LDP's internal mechanism to handle all these updates fail, causing traffic loss, and in the worst case, an LDP process crash due to memory exhaustion
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