VPP Logging Configuration

VPP logging is an important part of monitoring and troubleshooting the performance and behavior of the VPP dataplane.

VPP stores logs in two places:

/var/log/vpp.log — This file contains logs related to daemon startup and logs of commands executed directly via VPP CLI. Pay attention: VyOS does not use VPP CLI for configuration, so this log will not contain any configuration changes made via VyOS CLI and will not be informative in most cases.
System journal — contains logs related to the VPP daemon work, including errors, warnings, and informational messages. It is the main destination of logs generated by VPP.

Logging detail level can be configured via the next command:

set vpp settings logging default-level <level>

Where <level> can be one of the following:

emerg (Emergency) - System is unusable.
alert (Alert) - Immediate action required.
crit (Critical) - Critical conditions.
error (Error) - Error conditions.
warn (Warning) - Warning conditions.
notice (Notice) - Normal but significant.
info (Informational) - Routine informational messages.
debug (Debug) - Detailed debugging messages.
disabled (Disabled) - Logging disabled.

It is recommended to set logging level to debug only for troubleshooting purposes, as it can generate a large volume of log data. For regular operation, a level of info or warn is usually sufficient.

Troubleshooting

Improper logging configuration can lead to various issues, including:

Excessive log file sizes if the logging level is set too high (for example, debug).
Missing critical information if the logging level is set too low (for example, alert).
Performance degradation due to excessive logging overhead

Consider adjusting the logging level if you experience issues mentioned above.