VPP: Add comprehensive VPP documentation

This commit introduces extensive documentation for VyOS VPP (Vector Packet Processing)
Dataplane interfaces and features, including examples.

Features documented:
* VPP integration description, base requirements and limitations
* VPP dataplane core settings
* Features enabled in the dataplane: ACL, IPsec, NAT, sFlow
* VPP interface types: bonding, bridge, GRE, IPIP, kernel, loopback, VXLAN, XConnect

Note: This is an initial documentation version that will require ongoing improvements
based on user feedback and questions, real-world deployment testing and validation, additional
use cases and configuration scenarios discovered in production. Therefore, all pages are
marked as "need improvement".

1 files changed, 42 insertions, 0 deletions

diff --git a/docs/vpp/configuration/dataplane/logging.rst b/docs/vpp/configuration/dataplane/logging.rst
new file mode 100644
index 00000000..41da367a
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+++ b/docs/vpp/configuration/dataplane/logging.rst
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+:lastproofread: 2025-09-04
+
+.. _vpp_config_dataplane_logging:
+
+.. include:: /_include/need_improvement.txt
+
+#########################
+VPP Logging Configuration
+#########################
+
+VPP logging is an important part of monitoring and troubleshooting the performance and behavior of the VPP dataplane.
+
+VPP logs are stored in the ``/var/log/vpp.log`` file. Additionally daemon logs can be found in the system journal.
+
+Logging detalization can be configured via the next command:
+
+.. cfgcmd:: set vpp settings logging default-log-level <level>
+
+Where ``<level>`` can be one of the following:
+
+- ``emerg`` (Emergency) - System is unusable.
+- ``alert`` (Alert) - Immediate action required.
+- ``crit`` (Critical) - Critical conditions.
+- ``err`` (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.
+
+Potential Issues and Troubleshooting
+====================================
+
+Improper logging configuration can lead to various issues, including:
+
+- Excessive log file sizes if the logging level is set too high (e.g., ``debug``)
+- Missing critical information if the logging level is set too low (e.g., ``alert``)
+- Performance degradation due to excessive logging overhead
+
+Consider adjusting the logging level if you experience issues mentioned above.