pppdump

pppdump [options] [log_file...]

-r
    Raw output. Dumps the raw log data without interpretation, showing what pppdump received.

-s
    Summarize. Provides a brief summary of the connection parameters established during the PPP session.

-t
    Timestamp. Shows absolute timestamps for each log entry, rather than relative times or no times.

-v
    Verbose. Increases the verbosity of the output, showing more details about each parsed event.

-n
    No interpretation. Prevents interpretation of numeric values (e.g., protocol numbers), showing them as raw numbers instead of human-readable names.

-p
    Filter by protocol. Displays only messages related to a specific PPP protocol (e.g., LCP, IPCP, CHAP). Use -l to list available protocols.

-o
    Filter by option. Filters output to show messages related to a specific PPP option negotiated (e.g., MRU, authentication type). Use -l to list available options.

-f
    Filter by field. Filters output to show messages related to a specific field within a protocol message. Use -l to list available fields.

-i
    Filter by interface. Shows messages only for a specified network interface, if multiple interfaces are active or mentioned in the logs.

-u
    Filter by peer. Shows messages only for a specific peer, which could be identified by its IP address or hostname if logged.

-l
    List filters. Lists available protocol, option, field, interface, and peer filters that pppdump can recognize and filter by.

-h
    Help. Displays a brief help message showing command-line options and exits.

-V
    Version. Displays version information for pppdump and exits.

pppdump is a utility designed to parse and interpret the detailed debug output generated by the ppp daemon (pppd). When pppd is configured to log extensive debugging information (typically by enabling the debug option), its logs can become very verbose and challenging to read directly. pppdump transforms these raw, often cryptic, log entries into a more human-readable and structured format.

It's an invaluable tool for network administrators and developers troubleshooting Point-to-Point Protocol (PPP) connections. By analyzing the output, one can gain insight into the various phases of a PPP session, including Link Control Protocol (LCP) negotiation, authentication (PAP/CHAP), and Network Control Protocol (NCP) negotiations like IP Control Protocol (IPCP) for IP address assignment. It helps in identifying why a PPP link fails to establish, why authentication might be failing, or why network parameters aren't being correctly assigned.

pppdump can read log data from standard input or directly from specified log files, making it flexible for real-time monitoring via pipes or post-mortem analysis of archived logs. It provides options to filter by protocol, interface, or peer, allowing users to focus on specific aspects of the communication.

pppdump primarily relies on pppd's debug logging. If pppd is not run with sufficient debug options (e.g., by adding the debug keyword to its configuration), pppdump will have little or no meaningful information to process.

The output can be extremely verbose for long-running connections or high traffic, potentially making it hard to pinpoint specific issues without applying filters.

Interpretation accuracy might vary slightly with different pppd versions or non-standard log formats, though it generally handles standard pppd debug output well.

For pppdump to be effective, pppd must be configured to log detailed debug information. This is typically achieved by adding the debug option to pppd's configuration file (e.g., /etc/ppp/options or a peer-specific options file) or by passing it as a command-line argument when starting pppd. Without this, pppdump will not find the necessary diagnostic data in the logs.

Example: Add debug to /etc/ppp/options.

A common workflow involves piping the output of tail -f (for real-time monitoring) or cat (for file analysis) of the pppd log file into pppdump.

Example for real-time monitoring: tail -f /var/log/syslog | pppdump
Example for analyzing a log file: pppdump /var/log/ppp.log

pppdump is an integral part of the ppp package, which has been a cornerstone of Unix-like operating systems for implementing PPP connections since the early 1990s. Its development closely parallels that of pppd itself, providing a crucial debugging layer for a protocol that was, for decades, essential for dial-up internet access. While the dominance of dial-up has waned, pppdump remains relevant for diagnosing issues in modern PPP applications such as PPPoE (often used with DSL/fiber connections), PPTP, and L2TP VPNs. Its purpose has consistently been to demystify the complex state machine and negotiation processes of PPP, making it easier for system administrators to identify and resolve connectivity problems.

pppd(8), tail(1), grep(1), tcpdump(8)