Troubleshooting guide

3. Troubleshooting Functional Failures During Operation
151
3.24 Packet congestion in CPU processing does not recover
This section describes how to take actions if packet congestion in CPU processing is not cleared
up.
Packet congestion in CPU processing occurs due to the overflow of the input queue when the CPU
receives a large number of packets to be processed in software.
When packet congestion in CPU processing is detected, the following message is output:
E3 SOFTWARE 00003301 1000:000000000000 CPU congestion detected.
When packet congestion is cleared, the following message is output:
E3 SOFTWARE 00003302 1000:000000000000 CPU has recovered from congestion.
Packet congestion in CPU processing might occur even if the system is working normally such as
when the CPU receives a large number of packets with unknown destinations due to the aging of
routing information. If packet congestion is not cleared up or packet congestion occurs repeatedly,
the setting of the Switch or the network configuration might have a problem. When such an event
occurs, take action according to the following table.
Table 3-82: Action to take when packet congestion in CPU processing is not cleared
No. Items to check and commands Action
1 Identify packet types.
• Execute the
show netstat
statistics command at 20-second
intervals, and compare the results.
If the comparison shows that the count of the
total packets
received statistics item increases drastically for the ip or ip6
packet type, go to No. 2.
If the comparison shows that the count of the packets received
statistics item increases drastically for the arp packet type, go to
No. 2.
For other cases, go to No. 4.
2 Identify the VLAN interface that is
receiving the packets.
• Execute the
show netstat
interface command at 20-second
intervals, and compare the results.
If the comparison shows that the count of the Ipkts statistics item
increases drastically for a specific VLAN interface, go to No. 3.
For other cases, go to No. 4.
3 Identify the source and destination
addresses of the packets.
• For the VLAN interface identified in
No. 2, execute the
show tcpdump
interface command. Check the
source and destination addresses for
the packet type identified in No. 1.
If the packet type is
ip or ip6 and the destination address of the
target packets is the address of the Switch, the packets might be sent
incorrectly. Check the settings of the terminal that has the source
address or check the network configuration. Modify them so that
the target packets are not sent to the Switch.
If the packet type is
ip or ip6 and the destination address of the
target packets is the address of another device, the address of ARP
information might not be resolved or a large number of packets with
unknown destination might be sent.
• If the packet type is
ip, see 3.7.1 Communication is not
possible or is disconnected (5) Checking the ARP resolution
information with a neighboring device.
• If the packet type is
ip6, see 3.10.1 Communication is not
possible or is disconnected (5) Checking the NDP resolution
information with a neighboring device.