pppdump Command in Linux
The pppdump command in Linux converts the PPP (Point-to-Point Protocol) record file into a human-readable form. It processes raw PPP trace data created by the pppd daemon and converts it into a human-readable format. This is especially helpful for analyzing or debugging PPP (Point-to-Point Protocol) connections.
Table of Contents
Here is a comprehensive guide to the options available with the pppdump command in Linux −
Syntax of pppdump Command
The syntax of the Linux pppdump command is as follows −
pppdump [options] [files]
The [options] field in the above syntax is used to specify various options to modify the output. The [files] field is used to specify one or more record files to be processed.
pppdump Command Options
The options of the pppdump command are listed below −
| Options | Description |
|---|---|
| -h | Prints sent and received bytes in hexadecimal. Without -h or -p, bytes are printed as characters with escape sequences for non-printable ones. |
| -p | Groups sent and received bytes into PPP packets, interpreting async HDLC framing and checking the FCS. Packets are shown as hex values and characters (non-printable ones as '.'). |
| -d | With -p, decompresses packets compressed using BSD-Compress or Deflate methods. |
| -r | Reverses direction indicators, displaying 'sent' for received bytes/packets and 'rcvd' for sent ones. |
| -a | Displays absolute times. |
| -m mru | Uses the specified MRU (maximum receive unit) for both link directions when checking for over-length PPP packets with the -p option. |
Examples of pppdump Command in Linux
In this section, the usage of the pppdump command in Linux will be discussed with examples −
Converting a pppd Record File to a Human-Readable Form
To convert a pppd record file to a human-readable form, use the pppdump command with the record file path −
pppdump test_record
The above command converts a test record file from the current working directory. This reads the raw binary data from the record file (test_record) and outputs the frames in a readable format to the terminal.
Displaying the Absolute Timestamps
To display the absolute timestamps for each packet or byte, use the -a option −
pppdump -a test_record
Displaying the Output in Hexadecimal
To display the output bytes in the hexadecimal format, use the -h option. The following command sends and receives bytes as hexadecimal values instead of characters.
pppdump -h test_record
Grouping the Bytes in PPP Packets
To group the bytes in PPP packets, use the -p option with pppdump command −
pppdump -p test_record
The above command groups sent and received bytes into PPP packets. It also interprets the HDLC (High-Level Data Link Control) framing and checks the FCS (Frame Check Sequence).
Decompressing the PPP Packets
To decompress the PPP packets compressed with BSD-Compress or Deflate, use the -d option.
pppdump -p -d test_record
Reversing Direction Indicators
To reverse the labels for sent and received data, use the -r option −
pppdump -r test_record
Reversing the labels simplifies analysis, especially for debugging, interpreting logs, and cross-referencing data with other tools.
Specifying the Maximum Receive Units
To set the maximum receive units (mru), use the -m option with the pppdump command −
pppdump -p -m 1000 test_record
The above command sets the MRU to 1000 bytes when checking PPP packets.
Conclusion
The pppdump command in Linux simplifies the analysis and debugging of PPP (Point-to-Point Protocol) connections by converting raw PPP trace data into a readable format. It has various options for customizing the output such as grouping bytes into packets, displaying data in hexadecimal, decompressing compressed packets, and reversing direction indicators.
Examples demonstrate its practical use, including converting record files, displaying timestamps, and adjusting packet settings. In this tutorial, we covered he pppdump command, its syntax, options, and usage in Linux with examples.