Changing Encapsulation on Interfaces with Packet Capture Configured

Before modifying the encapsulation on a device interface that is configured for packet capture, you must disable packet capture and rename the latest packet capture file. Otherwise, packet capture saves the packets with different encapsulations in the same packet capture file. Packet files containing packets with different encapsulations are not useful, because packet analyzer tools like tcpdump cannot analyze such files.

After modifying the encapsulation, you can safely reenable packet capture on the router.

To change the encapsulation on packet capture-configured interfaces:

1. Disable packet capture following the steps in Disabling Packet Capture.
2. Commit the configuration.
3. Using the CLI, rename the latest packet capture file on which you are changing the encapsulation, with the .chdsl extension:
   1. From CLI operational mode, access the local UNIX shell:

      user@host> start shell

      %

   2. Navigate to the directory where packet capture files are stored:

      % cd /var/tmp

      %

   3. Rename the latest packet capture file for the interface on which you are changing the encapsulation—for example, fe.0.0.0:

      % mv pcap-file.fe.0.0.0 pcap-file.fe.0.0.0.chdsl

      %

   4. Return to the CLI operational mode:

      % exit

      user@host>

4. Change the encapsulation on the interface using the J-Web or CLI configuration editor.

   See instructions for configuring interfaces in the JUNOS Software Interfaces and Routing Configuration Guide

5. Commit the configuration.
6. Reenable packet capture following the steps in Enabling Packet Capture (Required).
7. Commit the configuration.