NEC IP8800/S3600 manual Neighboring system in 3.6.1 Communication Is Disabled or Is, Disconnected

3.Troubleshooting Functional Failures in Operation

3.22Congestion Caused by Packets Processed Through CPU Is Not Recovered

This section describes the procedure when congestion caused by packets requiring the handling of CPU is not recovered.

When a large amount of the packets requiring software process are received, the overflow on the receiving queue to CPU will cause the packet congestion.

The following message is displayed when the system detects packet congestion.

"E3 SOFTWARE 00003301 1000:000000000000 CPU congestion detected."

The following message is displayed when packet congestion is recovered.

"E3 SOFTWARE 00003302 1000:000000000000 CPU has recovered from congestion."

Congestion of packets handled by CPU might occurs even in a normal condition because of unexpected reason such as CPU received a large amount of unknown packets caused by routing information aging for temporary. If the packet congestion is not recovered or the packet congestion occurs and is recovered repeatedly, the settings of this system or the network configuration might be wrong. Take the following procedures while the problem occurs.

Table 3-70: Problems and Actions When CPU Packets Congestion is not Recovered

No.		Troubleshooting Steps and Command	Action
1	Determine the type of packets		Considering each of the results, if the count in "total packets received" as a
	•	Execute the show netstat	statistics item of "ip" or "ip6" in the packet type is drastically incremented,
		statistics command at an interval of 20	go to No.2.
		seconds. Then, compare the results.	Considering each of the results, if the count in "packets received" as a
			statistics item of "arp" in the packet type is drastically incremented, go to
			No.2.
			Otherwise, go to No.4.
2	Determine receiving VLAN interface		Considering each of the results, if the count in "Ipkts" as a statistics item in
	•	Execute the show netstat interface	a specific VLAN interface is drastically incremented, go to No.3.
		command at an interval of 20 seconds. Then,	Otherwise, go to No.4.
		compare the results.
3	Specify source and destination addresses for		If the destination address of packets whose packet type is "ip" or "ip6" is the
	packets		same as this system's address, the packet might be transmitted illegally.
	•	Execute the show tcpdump interface	Review the setting of the terminal having the source address or the network
		command against VLAN interface specified	configurations to keep the terminal from sending the packets to this system.
		in No.2. And then check to see source
			If the destination address of packets whose packet type is "ip" or "ip6" is the
		address and destination address in the packet
			same as other system's address, it might be considered that addresses in arp
		type specified in No.1.
			information are not be resolved or a large amount of unknown destination
			packets are received.
			• If packet type is "ip," see "(5)Checking ARP resolution information with
			neighboring system" in "3.6.1 Communication Is Disabled or Is
			Disconnected."
			• If packet type is "ip6," see "(4)Checking NDP resolution information with
			neighboring system" in "3.9.1 Communication Is Disabled or Is
			Disconnected."
			If packet type is "arp," a large amount of arp packets are being received. In
			this case, L2 loop might occur.
			Review the network configurations. If no problem is found in the network
			configuration, review the setting of the terminal having the source address.

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