CDRouter Support

Enable TCP & UDP Checksum Validation in CDRouter's UI

knowledge-base version 13.3

When viewing CDRouter test results in the CDRouter UI, you may notice that Checksum field of decoded TCP and UDP packets is displayed with the words [validation disabled] next to it:

Checksum validation is a feature of the Wireshark open-source packet decoding library. CDRouter uses tshark (the non-graphical counterpart to Wireshark) to decode and display packet contents in the CDRouter user interface. Wireshark disables the TCP and UDP checksum validation feature of the decoder by default in order to save time and allow the decoder to provide the most relevant infomation in the shortest amount of time.

In order to enable TCP and UDP checksum validation in packets displayed by CDRouter, the corresponding Wireshark preferences must first be set for the root user. This can be done by launching the Wireshark application as root on your CDRouter system and selecting the Edit/Preferences menu item to open the Preferences window. Search for “TCP” and “UDP” in the protocol list and set checkbox for “Validate TCP [UDP] checksum if possible”, then click “OK”.

Note that it is import to change the settings for the root user. For most Linux systems, including the NTA1000, the user logged into the graphical desktop is someone other than “root”, and setting the Wireshark preferences may not have the desired effect in the CDRouter UI.

An alternative method to enable TCP/UDP checksum validation is to edit the Wireshark preferences file directly. On most Linux systems, the Wireshark preferences for the root user are stored in /root/.wireshark/preferences. Simply add the following two lines to the end of this file:

tcp.check\_checksum: TRUE
 udp.check\_checksum: TRUE

Note: if the preferences file or the .wireshark directory do not exist, you can create them first.

Once the preferences have been set, you must restart CDRouter for them to take effect:

sudo service cdrouter restart



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