Dell N3200-ON EMC Networking N-Series Switches CLI Reference Guide version 6.7 - Page 420

The rate limiting for unknown packets occurs on the internal CPU port and does not affect hardware based traffic routing/forwarding in any way. Typically, the switch examines the received packets in software to check if there is a forwarding entry, create a forwarding entry (e.g., add a L2 MAC address or ARP response), and then either discard the packet or software forward the packet (only occurs during the brief transitional period when the system is actively adding a hardware forwarding entry but the hardware is not yet updated). Processing delays for higher priority packets may occur when the internal CPU queue is continually kept busy handling low priority packets. This command does not affect the rate limits for control plane packets. It is almost never necessary to use this command to change from the default value. The use of this command should be restricted to situations in which moderate to high rates of unknown unicast/multicast are continually sent to the switch CPU as evidenced by the show process cpu command and where the ipMapForwardingTask or bcmL2X task is showing high CPU usage. This occurs most frequently in networks where a high number of ARPs are continually received on untrusted ports, high numbers of L2 stations are timing out and reappearing or multicast flooding is occurring in the network. If problems with L2, L3 or multicast learning occur after changing this value, set the rate limit back to the default value and take other steps to correct or mitigate the underlying network issue directly. Use the show system internal pktmgr command to show the configured value. Example The following example shows output with higher than normal CPU usage due to packets copied to the software forwarding task. console#show process cpu Memory Utilization Report status bytes free 1053933568 alloc 673873920 CPU Utilization: PID Name 5 Secs 60 Secs 300 Secs Layer 2 Switching Commands 420