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Cisco Bug: CSCuq14012 - MFIB stops updating multicast hardware hit counters

Last Modified

Sep 09, 2019

Products (8)

  • Cisco Nexus 7000 Series Switches
  • Cisco Nexus 7000 10-Slot Switch
  • Cisco Nexus 7000 4-Slot Switch
  • Cisco Nexus 7700 6-Slot Switch
  • Cisco Nexus 7700 18-Slot Switch
  • Cisco Nexus 7000 18-Slot Switch
  • Cisco Nexus 7000 9-Slot Switch
  • Cisco Nexus 7700 10-Slot Switch

Known Affected Releases

6.2(8a)

Description (partial)

Symptom:MFIB (Multicast forwarding information base) stops updating statistics for multicast routes.  As a results, the S,G corresponding to the multicast route times out.  Users will see the multicast route constantly timing out and being rebuilt.  

Checking MRIB (multicast routing information base) statistics will always show zero hits against the multicast route:

n77a-core1# show forwarding multicast route source 10.2.1.2 group 239.1.1.1 module 9

  (10.2.1.2/32, 239.1.1.1/32), RPF Interface: Vlan2, flags:
    Received Packets: 0 Bytes: 0
    Number of Outgoing Interfaces: 1
    Outgoing Interface List Index: 1
      Vlan3 Outgoing Packets:0 Bytes:0  <---- counts are always zero

Conditions:This has been observed under the following sequence of steps:

1) New module added to a chassis (all interfaces unallocated)
2) Perform ISSU 
3) After ISSU, allocate interfaces to VDC.  At this point, multicast statistics for traffic hitting the forwarding engine for the newly allocated interface will not increment
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