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Cisco Bug: CSCvh77171 - N7K M2 - multicast traffic to CPU blackholed due to RL and CoPP dropping all packets

Last Modified

Aug 13, 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 7700 10-Slot Switch
  • Cisco Nexus 7000 9-Slot Switch

Known Affected Releases

6.2(14)

Description (partial)

Symptom:
The first multicast packet for a particular group needs to be sent to CPU for s,g state creation and subsequent hw adj creation. Such types of packet are being double accounted for - they hit CoPP (class copp-normal) and then the L3 mcast directly connected RL. 

The problem is that even policer dropped packets are hitting this RL creating a situation where no packets are leaked to CPU (combined drop of RL and CoPP) and the CoPP class gets completely exhausted, leading to ARP being starved (since it is in same CoPP class)

Conditions:
High rate of multicast traffic that has no s,g on the N7K.
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