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, 28 insertions, 0 deletions

diff --git a/docs/vpp/configuration/dataplane/l2learn.rst b/docs/vpp/configuration/dataplane/l2learn.rst
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+:lastproofread: 2025-09-04
+
+.. _vpp_config_dataplane_l2learn:
+
+.. include:: /_include/need_improvement.txt
+
+#########################
+VPP L2LEARN Configuration
+#########################
+
+When VPP dataplane is connected to a L2 domain, it needs to learn MAC addresses of devices connected to the domain. And the amount of MAC addresses that can be learned is limited by default.
+
+The limit can be configured using the following command:
+
+.. cfgcmd:: set vpp settings l2learn limit <value>
+
+This parameter configures the maximum number of MAC addresses that can be learned in the L2 domain. If you have a large number of devices, you may need to increase this limit to ensure all MAC addresses can be learned.
+
+Potential Issues and Troubleshooting
+====================================
+
+Improper L2LEARN configuration can lead to various issues, including:
+
+- Inability to learn all MAC addresses in the L2 domain if the limit is set too low
+- Increased packet loss or latency for devices that are not learned
+- Overall instability of the dataplane when handling L2 traffic
+
+Consider increasing the L2LEARN limit if you experience issues with MAC address learning or if you have a large number of devices in the L2 domain.