feat: activate 106 visual-validated canaries via swap

Imports 105 MD files (plus quick-start already present) from
origin/myst/current and adds them to docs/_swap.txt. The selection
is the BackstopJS visual-passers cohort: pages with <5% rendered
diff vs the live RST docs at docs.vyos.io/en/latest/, filtered to
those with an RST counterpart on current and no cmdincludemd usage
(template-format reconciliation pending).

Local sphinx-build with all 106 swapped: succeeded with 100
warnings (vs 95 baseline). The 5 new warnings are all undefined
cross-reference labels, not build failures:
- contributing/development.md (missing 'coding-guidelines')
- operation/upgrade-recovery.md (3 missing 'how_it_works' /
  'cancelling_recovery')
- vpp/configuration/dataplane/{buffers,memory,unix}.md (missing
  'vpp_config_dataplane_*' labels)

Source list: ~/.claude/projects/-Users-vybot-GitHub-vyos-documentation/docs/2026-04-29-myst-conversion-audit/visual-passers-under-5pct.txt
BackstopJS report: claude/gifted-hertz-74b9f9 worktree
(visual-compare/), 2026-04-23 vs vyos--1838.org.readthedocs.build.

🤖 Generated by [robots](https://vyos.io)

1 files changed, 120 insertions, 0 deletions

diff --git a/docs/vpp/configuration/interfaces/md-loopback.md b/docs/vpp/configuration/interfaces/md-loopback.md
new file mode 100644
index 00000000..bc65338b
--- /dev/null
+++ b/docs/vpp/configuration/interfaces/md-loopback.md
@@ -0,0 +1,120 @@
+---
+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:**
+```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:**
+```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:**
+```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
+```none
+# Create simple loopback
+set interfaces vpp loopback vpplo1
+set interfaces vpp loopback vpplo1 description "Router ID interface"
+```
+### Loopback with Kernel Interface
+```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)
+```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
+```