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, 87 insertions, 0 deletions

diff --git a/docs/configuration/interfaces/dummy.md b/docs/configuration/interfaces/dummy.md
new file mode 100644
index 00000000..d2d27c5d
--- /dev/null
+++ b/docs/configuration/interfaces/dummy.md
@@ -0,0 +1,87 @@
+---
+lastproofread: '2026-01-23'
+---
+
+(dummy-interface)=
+
+# Dummy
+
+A dummy interface is a virtual network interface that operates like the
+loopback interface, accepting traffic and routing it back to the local host.
+Unlike the loopback interface, which is limited to one per system and reserved
+for internal system use, multiple dummy interfaces can be created, removed, and
+managed without impacting core operations.
+
+As a software-based interface, the dummy interface does not depend on physical
+link state and remains active as long as the operating system is running.
+
+Dummy interfaces are commonly used in environments with multiple redundant
+uplinks (e.g., a server connected to two different switches), where assigning a
+management IP address to a specific physical interface is risky. If that
+interface fails, the management IP address becomes unreachable.
+
+Assigning the management IP address to a dummy interface and advertising it
+over all available physical links ensures the address remains reachable as long
+as at least one physical path is active.
+
+Dummy interfaces are also used for testing and simulation purposes.
+
+## Configuration
+
+### Common interface configuration
+
+```{cmdincludemd} /_include/interface-address.txt
+:var0: dummy
+:var1: dum0
+```
+
+```{cmdincludemd} /_include/interface-description.txt
+:var0: dummy
+:var1: dum0
+```
+
+```{cmdincludemd} /_include/interface-disable.txt
+:var0: dummy
+:var1: dum0
+```
+
+```{cmdincludemd} /_include/interface-vrf.txt
+:var0: dummy
+:var1: dum0
+```
+
+
+## Operation
+
+```{opcmd} show interfaces dummy
+
+Show brief interface information.
+
+:::{code-block} none
+vyos@vyos:~$ show interfaces dummy
+Codes: S - State, L - Link, u - Up, D - Down, A - Admin Down
+Interface        IP Address                        S/L  Description
+---------        ----------                        ---  -----------
+dum0             172.18.254.201/32                 u/u
+:::
+```
+
+```{opcmd} show interfaces dummy \<interface\>
+
+Show detailed interface information.
+
+:::{code-block} none
+vyos@vyos:~$ show interfaces dummy dum0
+dum0: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000
+    link/ether 26:7c:8e:bc:fc:f5 brd ff:ff:ff:ff:ff:ff
+    inet 172.18.254.201/32 scope global dum0
+       valid_lft forever preferred_lft forever
+    inet6 fe80::247c:8eff:febc:fcf5/64 scope link
+       valid_lft forever preferred_lft forever
+
+    RX:  bytes    packets     errors    dropped    overrun      mcast
+             0          0          0          0          0          0
+    TX:  bytes    packets     errors    dropped    carrier collisions
+       1369707       4267          0          0          0          0
+:::
+```
\ No newline at end of file