This article provides an explanation for misleading Multicast statistics when the show multicast route command is executed quickly in succession.
show multicast route
Constant and continuous traffic is egressing out for all Multicast groups. When the show multicast route extensive command is executed quickly in succession at an interval of 1-2 seconds, the kBps and pps statistics report the incorrect values.
show multicast route extensive
kBps and pps
and pps
pps
Example:
root@QFX5100> show multicast route instance Mcast-Group1 group 239.50.0.1 extensive | match stat Statistics: 3223 kBps, 3223 pps , 549101 packets Route state: Active Forwarding state: Forwarding root@QFX5100> show multicast route instance Mcast-Group1 group 239.50.0.1 extensive | match stat Statistics: 0 kBps, 0 pps , 549101 packets Route state: Active Forwarding state: Forwarding root@QFX5100> show multicast route instance Mcast-Group1 group 239.50.0.1 extensive | match stat Statistics: 2877 kBps, 2877 pps , 553037 packets Route state: Active Forwarding state: Forwarding root@QFX5100> show multicast route instance Mcast-Group1 group 239.50.0.1 extensive | match stat Statistics: 0 kBps, 0 pps , 553037 packets Route state: Active Forwarding state: Forwarding
This is an expected behavior on the QFX5100. In the current QFX5100 design, the statistics are fetched from hardware by the PFE and updated to the kernel. The kernel calculates the pps and kbps based on the timestamp, and this goes out of sync between kernel and PFE if the show command is given continuously.
Allow 10-15 seconds between the execution of the show commands.