capture-packet cpu

Function

The capture-packet cpu command captures packets sent to the CPU.

Format

capture-packet cpu [ vlan vlan-id | acl { ipv4-acl | ipv6 ipv6-acl } ] ^* destination { file file-name | terminal } ^* [ time-out time-out-value | packet-num number | packet-len length ] ^*

Parameters

Parameter	Description	Value
vlan vlan-id	Captures packets from a specified VLAN.	The value is an integer that ranges from 1 to 4094.
acl { ipv4-acl \| ipv6 ipv6-acl }	Captures packets matching a specified ACL or ACL6. NOTE: The specified ACL or ACL6 must exist and contain ACL rules. The destination IPv6 address should not be specified in rules of the ACL6 for the S2720-EI, S5720I-SI, S5720-LI, S5735-L, S5735S-L, S5735S-L-M, S5720S-LI, S5720S-SI, S5720-SI, S5735-S, S5735S-S, S5735-S-I, S5730S-EI, S5730-SI, S6720-LI, S6720S-LI, S6720S-SI, or S6720-SI. Otherwise, packets will fail to be captured.	ipv4-acl: The value is an integer in the range from 2000 to 5999 for the S5720-EI, S5720-HI, S5730-HI, S5731-H, S5731-S, S5731S-H, S5731S-S, S5732-H, S6720-EI, S6720-HI, S6720S-EI, S6730-H, S6730S-H, S6730-S, and S6730S-S, and from 2000 to 4999 for other models. ipv6 ipv6-acl: The value is an integer in the range from 2000 to 3999.
destination	Indicates the destination to which captured packet information is sent.	-
file file-name	Saves captured packet information to a file. The file name extension must be .cap.	The value is a string of 5 to 63 characters.
terminal	Displays captured packet information on a terminal.	-
time-out time-out-value	Specifies the timeout period for packet capture. The system stops capturing packets after the specified timeout period elapses.	The value is an integer that ranges from 1 to 300, in seconds. By default, the timeout period is 60s.
packet-num number	Specifies the number of packets to be captured. The system stops capturing packets after the specified number of packets are captured.	The value is an integer that ranges from 1 to 1000. The default value is 100.
packet-len length	Specifies the length of captured packets.	The value is an integer that ranges from 20 to 64, in bytes. The default value is 64 bytes.

Views

System view

Default Level

3: Management level

Usage Guidelines

Usage Scenario

When a CPU fault occurs (for example, the CPU usage is high), configure the packet capture function to capture packets sent to the CPU for analysis. This allows the switch to process invalid packets promptly, ensuring that the CPU works properly.

Precautions

If the IP addresses of ARP packets on the control plane match the IP addresses in a basic or advanced ACL, these ARP packets can also be captured.
Running this command will increase the CPU usage. Therefore, you are not advised to run this command if the CPU usage is higher than the specified value in a Warning message.
The packet capture configuration is not saved in the configuration file, and becomes invalid when packet capture is complete.
Different packet capture instances cannot be executed simultaneously. That is, a new packet capture instance can be executed only when the previous one is complete.
The system limits the rate of captured packets. The default rate limit is 64 kbit/s. If the rate of packets exceeds the limit, some packets may be discarded.

Example

# Capture the packets to be sent to the CPU, save them to the abc.cap file, and display them on the terminal.

<HUAWEI> system-view
[HUAWEI] capture-packet cpu destination file flash:/abc.cap
[HUAWEI]                                                    
  Packet: 1                                                                     
  -------------------------------------------------------                       
  01 80 c2 00 00 0e 00 e0 09 87 78 90 81 00 00 01                               
  88 cc 02 07 04 00 e0 09 87 78 90 04 16 05 47 69                               
  67 61 62 69 74 45 74 68 65 72 6e 65 74 34 2f 30                               
  2f 32 36 06 02 00 78 08 15 47 69 67 61 62 69 74                               
  -------------------------------------------------------                       
                                                                                
  Packet: 2                                                                     
  -------------------------------------------------------                       
  01 80 c2 00 00 0e 00 e0 09 87 78 90 81 00 00 01                               
  88 cc 02 07 04 00 e0 09 87 78 90 04 16 05 47 69                               
  67 61 62 69 74 45 74 68 65 72 6e 65 74 34 2f 30                               
  2f 32 36 06 02 00 78 08 15 47 69 67 61 62 69 74                               
  -------------------------------------------------------                       
                                                                                
  ------------------packet getting report-----------------------                
  file: flash:/abc.cap                                                         
  packets getting: cpu                                                          
  acl: -                                                                        
  vlan: -  cvlan: -                                                             
  car: -- timeout: 60s                                                          
  packets: 100 (expected) 2 (actual)                                            
  length without tunnel header: 64 (expected)                                                         
  -------------------------------------------------------

**Table 1** Description of the **capture-packet cpu** command output
Item	Description
Packet: i	ith captured packet.
file	Local path that stores captured packets. If NULL is displayed, captured packets are displayed on a terminal, instead of being saved to a specified file.
packets getting	The system captures the packets to be sent to the CPU.
acl	ACL number matched by captured packets.
acl ipv6	ACL6 number matched by captured packets.
vlan	VLAN ID of captured packets.
cvlan	Inner VLAN ID of captured packets.
car	Rate of captured packets.
timeout	Timeout period of packet capture. The system stops capturing packets after the specified timeout period elapses.
packets	expected: number of packets expected to be captured actual: actual number of captured packets
length without tunnel header	Length of captured packets, excluding the length of tunnel headers.