Using J-Web Packet Capture

To use J-Web packet capture:

Select Troubleshoot > Packet Capture.

Note: After you make changes to the configuration in this window, you must commit the changes immediately for them to take effect. To commit all changes to the active configuration, select Commit Options > Commit. See Using the Commit Options to Commit Configuration Changes (J-Web Procedure) for details about all commit options.

Enter information into the Packet Capture page (Figure 31) as described in Table 77.
The sample configuration in Table 77 captures the next 10 TCP packets originating from the IP address 10.1.40.48 on port 23 and passing through the Gigabit Ethernet interface ge-0/0/0.
To save the captured packets to a file, or specify other advanced options, click the expand icon next to Advanced options, and enter information as described in Table 77.
Click Start.
The captured packet headers are decoded and displayed in the Packet Capture display (see Figure 32).
Table 78 summarizes the output fields of the display.
Do one of the following:
- To stop capturing the packets and stay on the same page while the decoded packet headers are being displayed, click Stop Capturing.
- To stop capturing packets and return to the Packet Capture page, click OK.

Figure 31: Packet Capture Page

Table 77: Packet Capture Field Summary

Field	Function	Your Action
Interface	Specifies the interface on which the packets are captured. If you select default, packets on the Ethernet management port 0, are captured.	From the list, select an interface; for example, ge-0/0/0.
Detail level	Specifies the extent of details to be displayed for the packet headers. Brief—Displays the minimum packet header information. This is the default. Detail—Displays packet header information in moderate detail. Extensive—Displays the maximum packet header information.	From the list, select Detail.
Packets	Specifies the number of packets to be captured. Values range from 1 to 1000. Default is 10. Packet capture stops capturing packets after this number is reached.	From the list, select the number of packets to be captured; for example, 10.
Addresses	Specifies the addresses to be matched for capturing the packets using a combination of the following parameters: Direction—Matches the packet headers for IP address, hostname, or network address of the source, destination or both. Type—Specifies if packet headers are matched for host address or network address. You can add multiple entries to refine the match criteria for addresses.	Select address-matching criteria. For example: From the Direction list, select src. From the Type list, select host. In the Address box, type 10.1.40.48. Click Add.
Protocols	Matches the protocol for which packets are captured. You can choose to capture TCP, UDP, or ICMP packets or a combination of TCP, UDP, and ICMP packets.	From the list, select a protocol; for example, tcp.
Ports	Matches packet headers containing the specified source or destination TCP or UDP port number or port name.	Select a direction and a port. For example: From the Type list, select src. In the Port box, type 23.
Advanced Options
Absolute TCP Sequence	Specifies that absolute TCP sequence numbers are to be displayed for the packet headers.	To display absolute TCP sequence numbers in the packet headers, select this check box. To stop displaying absolute TCP sequence numbers in the packet headers, clear this check box.
Layer 2 Headers	Specifies that link-layer packet headers will be displayed.	To include link-layer packet headers while capturing packets, select this check box. To exclude link-layer packet headers while capturing packets, clear this check box.
Non-Promiscuous	Specifies not to place the interface in promiscuous mode, so that the interface reads only packets addressed to it. In promiscuous mode, the interface reads every packet that reaches it.	To read all packets that reach the interface, select this check box. To read only packets addressed to the interface, clear this check box.
Display Hex	Specifies that packet headers, except link-layer headers, are to be displayed in hexadecimal format.	To display the packet headers in hexadecimal format, select this check box. To stop displaying the packet headers in hexadecimal format, clear this check box.
Display ASCII and Hex	Specifies that packet headers are to be displayed in hexadecimal and ASCII format.	To display the packet headers in ASCII and hexadecimal formats, select this check box. To stop displaying the packet headers in ASCII and hexadecimal formats, clear this check box.
Header Expression	Specifies the match condition for the packets to be captured. The match conditions you specify for Addresses, Protocols, and Ports are displayed in expression format in this field.	You can enter match conditions directly in this field in expression format or modify the expression composed from the match conditions you specified for Addresses, Protocols, and Ports. If you change the match conditions specified for Addresses, Protocols, and Ports again, packet capture overwrites your changes with the new match conditions.
Packet Size	Specifies the number of bytes displayed for each packet. If a packet header exceeds this size, the display is truncated for the packet header. The default value is 96 bytes.	Type the number of bytes you want to capture for each packet header; for example, 256.
Don't Resolve Addresses	Specifies that IP addresses are not resolved into hostnames in the packet headers displayed.	To prevent packet capture from resolving IP addresses to hostnames, select this check box. To resolve IP addresses into hostnames, clear this check box.
No Timestamp	Suppresses the display of packet header timestamps.	To stop displaying timestamps in the captured packet headers, select this check box. To display the timestamp in the captured packet headers, clear this check box.
Write Packet Capture File	Writes the captured packets to a file in PCAP format in /var/tmp. The files are named with the prefix jweb-pcap and the extension .pcap. If you select this option, the decoded packet headers are not displayed on the packet capture page.	To save the captured packet headers to a file, select this check box. To decode and display the packet headers on the J-Web page, clear this check box.