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Cisco Bug: CSCvv36949 - J2 comp: MPLS packet (inner L2 payload) with TTL 255 being trapped as IPv4 TTL 0 on J2

Last Modified

Oct 02, 2020

Products (1)

  • Cisco Network Convergence System 5500 Series

Known Affected Releases

7.2.1.BASE

Description (partial)

Symptom:
MPLS packet with 2 labels, outer SR transport and inner EVPN service label, dropped by core router due to wrongly treating them as  IPv4 TTL 0 packets.

RP/0/RP0/CPU0:Fretta-DCI-PE4#sh controllers npu stats traps-all instance all location 0/3/CPU0 | i Ttl         
RxTrapIpv4Ttl0                                0    108  0x6c        32010   517232               256594651       << increments seen     
bcmRxTrapTerminatedIpv4Ttl0                   0    109  0x6d        32010   0                    0                    
RxTrapIpv4Ttl1                                0    112  0x70        32010   0                    0                    
bcmRxTrapTerminatedIpv4Ttl1                   0    113  0x71        32010   0                    0                    
RxTrapMplsTtl1Terminated                      0    143  0x8f        32014   0                    0                    
RxTrapIpv4Ttl0                                1    108  0x6c        32010   0                    0                    
bcmRxTrapTerminatedIpv4Ttl0                   1    109  0x6d        32010   0                    0                    
RxTrapIpv4Ttl1                                1    112  0x70        32010   0                    0                    
bcmRxTrapTerminatedIpv4Ttl1                   1    113  0x71        32010   0                    0                    
RxTrapMplsTtl1Terminated                      1    143  0x8f        32014   0                    0                    
RP/0/RP0/CPU0:Fretta-DCI-PE4#

Conditions:
EVPN service end to end. Core router has J2 in compatibility mode, receiving 2 label MPLS packets from the imposition PE router. The drops are seen only when the customer packet DMAC starts with 00.
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