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Cisco Bug: CSCvs53822 - Local Multicast stops forwarding on TRM vPC VTEPs

Last Modified

Jun 23, 2020

Products (61)

  • Cisco Nexus 9000 Series Switches
  • Cisco Nexus 9516 Switch
  • Cisco Nexus 3548-X Switch
  • Cisco Nexus 3636C-R Switch
  • Cisco Nexus 92348GC-X Switch
  • Cisco Nexus 3548 Switch
  • Cisco Nexus 93108TC-FX Switch
  • Cisco Nexus 92160YC-X Switch
  • Cisco Nexus 9396PX Switch
  • Cisco Nexus 31108TC-V Switch
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Known Affected Releases

9.3(2)

Description (partial)

Symptom:
Local multicast connected to vPC VTEPs using TRM stop forwarding multicast after some time.

Conditions:
N9K VPC TRM VXLAN

The part that seemed to be failing is that L2 M2RIB was not getting pushed correctly to L2 MFDM as we could see that Po75 for VLAN 84 was missing:
 
N9K# show forwarding distribution l2 multicast ip-based vlan 84 group 239.1.0.1
Vlan: 84, Group: 239.1.0.1, Source: 0.0.0.0
  Outgoing Interface List Index: 168
  Reference Count: 42
  Num L3 usages: 32
  Platform Index: 0xae0061
  Vpc peer link exclude flag set
  VXLAN Vlan: 84
  Number of Outgoing Interfaces: 3   <<<<<< port-channel75 missing
    port-channel53
    port-channel97
    nve1
 
Some of the issues that we noticed is that we were seeing continuous failures for ?Number of L2 index alloc failed? for MFDM:
N9K# show system internal mfdm info statistics  | i fail
Number of stat rsp send failure to mrib            :0
Number of send failure to mfib                     :0
Number of L3 index alloc failed                    :0
Number of L2 index alloc failed                    :95619       <<<< constantly increasing
 
MERSW12%VRF_CORP# show system internal mfdm info statistics  | i fail
Number of stat rsp send failure to mrib            :0
Number of send failure to mfib                     :0
Number of L3 index alloc failed                    :0
Number of L2 index alloc failed                    :95883        <<<< constantly increasing
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