FAQ-Why Ping Packets Especially Large Ping Packets Are Lost Sometimes?

Publication Date:  2014-09-15 Views:  394 Downloads:  0
Issue Description
FAQ-Why Ping Packets Especially Large Ping Packets Are Lost Sometimes?
Alarm Information
None
Handling Process
FAQ-Why Ping Packets Especially Large Ping Packets Are Lost Sometimes?

This problem is caused by the CPU protection mechanism. The CPU protection mechanism processes ICMP packets as follows:

The software limits the rate of ICMP packets.
The icmp rate-limit { total | interface interface-type interface-number [ to interface-number ] } threshold threshold-value command limits the rate of ICMP packets on each GE interface to 20 pps and on the device to 100 pps by default. When the number of ICMP packets sent by an interface every second exceeds the rate threshold, the system delivers an ACL. The ACL discards all the ICMP packets with the MAC address as the device's MAC address. After two minutes, the device is restored. This process continues. You can run the undo icmp rate-limit { total | interface interface-type interface-number [ to interface-number ] }} command to cancel rate limiting.
The system limits the rate of ICMP packets sent to the CPU.
The rate limit of ICMP packets sent to the CPU is 128 kbit/s. Assume that the packet size is 1024 bytes. Only 16 packets can be sent to the CPU within 1s, that is, a packet is sent every 62.5 ms. If a packets is sent at the rate grater than 62.5 ms, the packet is discarded. Assume that the packet size is 64 bytes. Only 256 packets can be sent to the CPU within 1s, that is, a packet is sent every 4 ms.
Root Cause
None
Suggestions
None

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