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3. Troubleshooting Functional Failures in Operation
124
3.22 Congestion 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
• Execute the show netstat
statistics command at an interval of 20
seconds. Then, compare the results.
Considering each of the results, if the count in "total packets received" as a
statistics item of "ip" or "ip6" in the packet type is drastically incremented,
go to No.2.
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
• Execute the show netstat interface
command at an interval of 20 seconds. Then,
compare the results.
Considering each of the results, if the count in "Ipkts" as a statistics item in
a specific VLAN interface is drastically incremented, go to No.3.
Otherwise, go to No.4.
3 Specify source and destination addresses for
packets
• Execute the show tcpdump interface
command against VLAN interface specified
in No.2. And then check to see source
address and destination address in the packet
type specified in No.1.
If the destination address of packets whose packet type is "ip" or "ip6" is the
same as this system's address, the packet might be transmitted illegally.
Review the setting of the terminal having the source address or the network
configurations to keep the terminal from sending the packets to this system.
If the destination address of packets whose packet type is "ip" or "ip6" is the
same as other system's address, it might be considered that addresses in arp
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.