View the statistics of the forwarded packets and bytes, and the dropped packets and bytes for the traffic sent toward CP. The queue assignment is based on the protocol types, not on the internal CoS value. These statistics are useful for debugging purposes.
When a neighbor transitions to the STALE state, to initiate Neighbor Unreachability detection (NUD), a duplicate copy of the traffic destined to this neighbor is sent to the switch Control Processor (CP) on a low priority queue (queue 0). The original packet is forwarded to this neighbor. Once NUD is initiated, the hardware records are updated and the traffic is no longer sent to the CP. When a high rate of such traffic is sent to CP, the switch can drop some of these packets due to the in built CP rate limiting feature, which protects the CP from DOS attacks.
Use the command show qos cosq-stats cpu-port to view drop statistics on the CPU queue. This design does not result in loss of traffic.
Use the command ipv6 nd reachable-time <0-3600000> to increase the default value of 3000 milliseconds which in turn delays the scenario of data path sending STALE neighbor destined packets to the CP.
Note
If you disable rate limiting on queue 6, bandwidth is shared based on the weights from queues 0 through 6. Based on equal weights assigned for queues 4 through 6, equal amounts of traffic egress queues 4 through 6. The system displays Queue 6 to provide much lower throughput than 50% of port bandwidth.
show qos cosq-stats cpu-port
Note
Product Notice: The show command output varies based on your hardware platform. On all platforms except VSP 8600 Series, the show command output displays Out Packets and Out Bytes per interface which shows the number of unicast packets sent out on each queue for an egress port. VSP 8600 Series uses VoQ queuing architecture which supports an increased number of available queues, hence the output displays the number of packets accepted and dropped on each protocol type going to the CPU.