feat: flip swap mechanism — MD as primary, RST as override (Phase 1)

This is the first of three phases inverting the per-page swap mechanism
so MD becomes the canonical primary and RST becomes the rare override.

Phase 1 — file renames + conf.py exclude_patterns flip only:
- Rename docs/**/md-<stem>.md to docs/**/<stem>.md (drop md- prefix)
  for all 254 stems previously listed in docs/_swap.txt
- Rename docs/**/<stem>.rst to docs/**/rst-<stem>.rst (add rst- prefix)
  for the same 254 stems
- Repurpose docs/_swap.txt as docs/_rst_overrides.txt; initially empty
  comment-only since no pages need the RST fallback right now
- conf.py exclude_patterns flipped: rst-*.rst is now excluded by default
  instead of md-*.md
- conf.py runtime-artifact references updated to _rst_override_state.json
  and _md_exclude.txt (Phase 2 will rewrite swap_sources.py to produce
  these names; for now no swap script runs because overrides list is empty)

Phase 2 (next commit on this branch) will rewrite scripts/swap_sources.py
with inverted rename direction, delete scripts/import_myst.py + tests, and
update tests/test_swap_sources.py for the new semantics.

Phase 3 will be the cleanup pass and ready-for-review flip.

Generated by robots https://vyos.io

1 files changed, 154 insertions, 0 deletions

diff --git a/docs/vpp/configuration/interfaces/rst-loopback.rst b/docs/vpp/configuration/interfaces/rst-loopback.rst
new file mode 100644
index 00000000..61ef6aca
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+++ b/docs/vpp/configuration/interfaces/rst-loopback.rst
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+:lastproofread: 2026-03-13
+
+.. _vpp_config_interfaces_loopback:
+
+.. include:: /_include/need_improvement.txt
+
+####################################
+VPP Loopback Interface Configuration
+####################################
+
+VPP loopback interfaces provide virtual interfaces that remain
+administratively up and are commonly used for stable addressing,
+routing protocols, and as Bridge Virtual Interfaces (BVI). Loopback
+interfaces in VPP offer high-performance virtual connectivity with optimized
+packet processing.
+
+Basic Configuration
+-------------------
+
+Creating a Loopback Interface
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. cfgcmd:: set interfaces vpp loopback <vpploN>
+
+   Create a loopback interface where ``<vpploN>`` follows the naming
+   convention ``vpplo1``, ``vpplo2``, etc.
+
+**Basic Example:**
+
+.. code-block:: none
+
+   set interfaces vpp loopback vpplo1
+
+Interface Configuration
+-----------------------
+
+Description and Administrative Control
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. cfgcmd:: set interfaces vpp loopback <vpploN> description <description>
+
+   Set a descriptive name for the loopback interface.
+
+.. cfgcmd:: set interfaces vpp loopback <vpploN> disable
+
+   Administratively disable the loopback interface.
+
+Kernel Interface Integration
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Kernel interface is bounded to the VPP loopback interface for management
+and application compatibility.
+
+IP Address Configuration
+------------------------
+
+.. cfgcmd:: set interfaces vpp loopback <vpploN> address <ip-address/prefix>
+
+   Configure IPv4 or IPv6 addresses on the kernel interface. Multiple
+   addresses can be assigned.
+
+**Examples:**
+
+.. code-block:: none
+
+   # IPv4 address
+   set interfaces vpp loopback vpplo1 address 192.168.1.10/24
+
+   # IPv6 address
+   set interfaces vpp loopback vpplo1 address 2001:db8::10/64
+
+MTU Configuration
+-----------------
+
+.. cfgcmd:: set interfaces vpp loopback <vpploN> mtu <size>
+
+   Set the Maximum Transmission Unit (MTU) for the kernel interface.
+   The MTU must be compatible with the connected VPP interface.
+
+VLAN Configuration
+------------------
+
+VPP kernel interfaces support VLAN (Virtual LAN) sub-interfaces for network
+segmentation.
+
+Creating VLAN Sub-interfaces
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. cfgcmd:: set interfaces vpp loopback <vpploN> vif <vlan-id>
+
+   Create a VLAN sub-interface with the specified VLAN ID (0-4094).
+
+VLAN Sub-interface Configuration
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+VLAN sub-interfaces support the same configuration options as the parent
+interface:
+
+.. cfgcmd:: set interfaces vpp loopback <vpploN> vif <vlan-id> address
+   <ip-address/prefix>
+
+.. cfgcmd:: set interfaces vpp loopback <vpploN> vif <vlan-id> description
+   <description>
+
+.. cfgcmd:: set interfaces vpp loopback <vpploN> vif <vlan-id> disable
+
+.. cfgcmd:: set interfaces vpp loopback <vpploN> vif <vlan-id> mtu <size>
+
+**Examples:**
+
+.. code-block:: none
+
+   # Configure VLAN 100
+   set interfaces vpp loopback vpplo1 vif 100 address 192.168.100.1/24
+   set interfaces vpp loopback vpplo1 vif 100 description "Management VLAN"
+   set interfaces vpp loopback vpplo1 vif 100 mtu 1500
+
+   # Configure VLAN 200
+   set interfaces vpp loopback vpplo1 vif 200 address 192.168.200.1/24
+   set interfaces vpp loopback vpplo1 vif 200 description "Guest VLAN"
+
+Configuration Examples
+----------------------
+
+Basic Loopback Interface
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. code-block:: none
+
+   # Create simple loopback
+   set interfaces vpp loopback vpplo1
+   set interfaces vpp loopback vpplo1 description "Router ID interface"
+
+Loopback with Kernel Interface
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. code-block:: none
+
+   # Loopback with management access
+   set interfaces vpp loopback vpplo2
+   set interfaces vpp loopback vpplo2 description "Management loopback"
+   set interfaces vpp loopback vpplo2 address 10.255.255.1/32
+
+Bridge Virtual Interface (BVI)
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. code-block:: none
+
+   # Loopback as BVI for bridge
+   set interfaces vpp loopback vpplo3
+   set interfaces vpp loopback vpplo3 description "Bridge gateway interface"
+   set interfaces vpp bridge vppbr1
+   set interfaces vpp bridge vppbr1 member interface vpplo3 bvi
+   set interfaces vpp loopback vpplo3 address 192.168.100.1/24