refactor(swap): rename imported .md files to md- prefix for swap mechanism

Restore the canary file naming convention that swap_sources.py expects:
the imported MyST pages now live as docs/<dir>/md-<name>.md alongside
the existing docs/<dir>/<name>.rst, so swap_sources.py --swap can rename
them into place at build time.

- 254 .md files renamed (every page with a matching .rst counterpart)
- 2 MyST-only pages left at their final names (no .rst exists, no swap
  needed): docs/copyright.md, docs/automation/terraform/terraformvyos.md

All 114 stems listed in docs/_swap.txt now have a corresponding
md-<name>.md source file ready to swap in.

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

1 files changed, 79 insertions, 0 deletions

diff --git a/docs/configuration/protocols/md-igmp-proxy.md b/docs/configuration/protocols/md-igmp-proxy.md
new file mode 100644
index 00000000..961f921b
--- /dev/null
+++ b/docs/configuration/protocols/md-igmp-proxy.md
@@ -0,0 +1,79 @@
+---
+lastproofread: '2023-11-13'
+---
+
+(igmp-proxy)=
+
+# IGMP Proxy
+
+{abbr}`IGMP (Internet Group Management Protocol)` proxy sends IGMP host messages
+on behalf of a connected client. The configuration must define one, and only one
+upstream interface, and one or more downstream interfaces.
+
+## Configuration
+
+```{cfgcmd} set protocols igmp-proxy interface \<interface\> role \<upstream | downstream\>
+
+* **upstream:** The upstream network interface is the outgoing interface
+which is responsible for communicating to available multicast data sources.
+There can only be one upstream interface.
+
+* **downstream:** Downstream network interfaces are the distribution
+interfaces to the destination networks, where multicast clients can join
+groups and receive multicast data. One or more downstream interfaces must
+be configured.
+```
+
+```{cfgcmd} set protocols igmp-proxy interface \<interface\> alt-subnet \<network\>
+
+Defines alternate sources for multicasting and IGMP data. The network address
+must be on the following format 'a.b.c.d/n'. By default, the router will
+accept data from sources on the same network as configured on an interface.
+If the multicast source lies on a remote network, one must define from where
+traffic should be accepted.
+
+This is especially useful for the upstream interface, since the source for
+multicast traffic is often from a remote location.
+
+This option can be supplied multiple times.
+```
+
+```{cfgcmd} set protocols igmp-proxy disable-quickleave
+
+Disables quickleave mode. In this mode the daemon will not send a Leave IGMP
+message upstream as soon as it receives a Leave message for any downstream
+interface. The daemon will not ask for Membership reports on the downstream
+interfaces, and if a report is received the group is not joined again the
+upstream.
+
+If it's vital that the daemon should act exactly like a real multicast client
+on the upstream interface, this function should be enabled.
+
+Enabling this function increases the risk of bandwidth saturation.
+```
+
+```{cfgcmd} set protocols igmp-proxy disable
+
+Disable this service.
+```
+
+(igmp-proxy-example)=
+
+### Example
+
+Interface eth1 LAN is behind NAT. In order to subscribe 10.0.0.0/23 subnet
+multicast which is in eth0 WAN we need to configure igmp-proxy.
+
+```none
+set protocols igmp-proxy interface eth0 role upstream
+set protocols igmp-proxy interface eth0 alt-subnet 10.0.0.0/23
+set protocols igmp-proxy interface eth1 role downstream
+```
+
+
+## Operation
+
+```{opcmd} restart igmp-proxy
+
+Restart the IGMP proxy process.
+```
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