Example for Configuring a Device to Obtain Packet Headers Sent to its CPU

This section provides an example for configuring a device to obtain packet headers sent to its central processing unit (CPU).

Networking Requirements

As shown in Figure 1, PC1 accesses the Internet over Device A and Device B. Device B has high CPU usage. To find out the reason why Device B has high CPU usage, configure Device B to obtain packet headers sent to its CPU.

Figure 1 Configuring Device B to obtain packet headers sent to its CPU

Interfaces 1 through 3 in this example represent GE 0/1/0, GE 0/1/1, and GE 0/1/2, respectively.

Configuration Roadmap

The configuration roadmap is as follows:

Configure the function of obtaining packet headers sent to Device B's CPU.

Data Preparation

To complete the configuration, you need the following data:

Interface IP addresses
Packet header obtaining timeout time and number of obtained packet headers

Procedure

Configure interface IP addresses and routing protocol. The configuration details are not provided.

Configure Device B to obtain packet headers sent to its CPU.

<DeviceB> capture-packet local-host all interface gigabitethernet 0/1/2 packet-len 60 packet-num 1000 time-out 3600

View the configuration and the packet header obtaining file.

# View the configuration.

<DeviceB> display capture-packet config-state
Capture-Packet Index 1
Type        : local-host
SysID       : all
Interface   : GigabitEthernet0/1/2
File Name   : cfcard:/capture_host_all_GigabitEthernet3.0.2_2012-05-03-10-51-29.cap
Time-out    : 3600 seconds
Packet-num  : 1000
Packet-len  : 60
BufferOnly  : disabled

# View the packet header obtaining file.

<DeviceB> display capture-packet file cfcard:/capture_host_all_GigabitEthernet3.0.2_2012-05-03-10-51-29.cap
a1 b2 c3 d4 00 02 00 04 00 00 00 00 00 00 00 00
00 00 ff ff 00 00 00 09 4d 10 36 db 00 0a d5 81
00 00 00 0c 00 00 00 0c ff 03 c0 21 09 9d 00 08
8a 8c bc c3 4d 10 36 db 00 0a d6 ae

Configuration Files

Device A configuration file

#
sysname DeviceA
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 10.1.1.2 255.255.255.0
#
interface GigabitEthernet0/1/1
 undo shutdown
 ip address 10.1.2.1 255.255.255.0
#
ospf 1
 area 0.0.0.0
  network 10.1.1.0 0.0.0.255
  network 10.1.2.0 0.0.0.255
#
return

Device B configuration file

#
sysname DeviceB
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 10.1.1.1 255.255.255.0
#
interface GigabitEthernet0/1/2
 undo shutdown
 ip address 10.1.5.1 255.255.255.0
#
ospf 1
 area 0.0.0.0
  network 10.1.1.0 0.0.0.255
  network 10.1.5.0 0.0.0.255
#
return