You can use the J-Web packet capture diagnostic tool when you need to quickly capture and analyze router control traffic on a device. Packet capture on the J-Web interface allows you to capture traffic destined for or originating from the Routing Engine. You can use J-Web packet capture to compose expressions with various matching criteria to specify the packets that you want to capture. You can either choose to decode and view the captured packets in the J-Web interface as they are captured, or save the captured packets to a file and analyze them offline using packet analyzers such as Ethereal. J-Web packet capture does not capture transient traffic.
Alternatively you can use the CLI monitor traffic command to capture and display packets matching a specific criteria. For details, see the JUNOS Enhanced Services Administration Guide.
To capture transient traffic and entire IPv4 data packets for offline analysis, you must configure packet capture with the J-Web or CLI configuration editor. For details, see the JUNOS Enhanced Services Administration Guide.
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