feat(swap): import .md files and webp transition from myst/current

Selective import from origin/myst/current (cf9c9b34):
- Add/update 255 .md files (full MyST conversion plus webp ref updates)
- Delete 175 PNG/JPG from docs/_static/images (webp twins already present)
- Delete 5 autotest topology.png (webp twins already present)

Preserved on swap (untouched):
- All .rst files (incremental swap pattern)
- conf.py, _ext/, _include/*.txt, .gitignore
- 115 canary md-*.md files
- 7 superpowers/specs/*.md design docs
- Logos vyos-logo.png / vyos-logo-icon.png (referenced by conf.py)

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

1 files changed, 205 insertions, 0 deletions

diff --git a/docs/configuration/protocols/bfd.md b/docs/configuration/protocols/bfd.md
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+---
+lastproofread: '2023-01-27'
+---
+
+```{include} /_include/need_improvement.txt
+```
+
+(routing-bfd)=
+
+# BFD
+
+{abbr}`BFD (Bidirectional Forwarding Detection)` is described and extended by
+the following RFCs: {rfc}`5880`, {rfc}`5881` and {rfc}`5883`.
+
+In the age of very fast networks, a second of unreachability may equal millions of lost packets.
+The idea behind BFD is to detect very quickly when a peer is down and take action extremely fast.
+
+BFD sends lots of small UDP packets very quickly to ensures that the peer is still alive.
+
+This allows avoiding the timers defined in BGP and OSPF protocol to expires.
+
+## Configure BFD
+
+```{cfgcmd} set protocols bfd peer \<address\>
+
+Set BFD peer IPv4 address or IPv6 address
+```
+
+```{cfgcmd} set protocols bfd peer \<address\> echo-mode
+
+Enables the echo transmission mode
+```
+
+```{cfgcmd} set protocols bfd peer \<address\> multihop
+
+Allow this BFD peer to not be directly connected
+```
+
+```{cfgcmd} set protocols bfd peer \<address\> source [address \<address\> | interface \<interface\>]
+
+Bind listener to specific interface/address, mandatory for IPv6
+```
+
+```{cfgcmd} set protocols bfd peer \<address\> interval echo-interval \<10-60000\>
+
+The minimal echo receive transmission interval that this system is
+capable of handling
+```
+
+```{cfgcmd} set protocols bfd peer \<address\> interval multiplier \<2-255\>
+
+Remote transmission interval will be multiplied by this value
+```
+
+```{cfgcmd} set protocols bfd peer \<address\> interval [receive | transmit] \<10-60000\>
+
+Interval in milliseconds
+```
+
+```{cfgcmd} set protocols bfd peer \<address\> shutdown
+
+Disable a BFD peer
+```
+
+```{cfgcmd} set protocols bfd peer \<address\> minimum-ttl \<1-254\>
+
+For multi hop sessions only. Configure the minimum expected TTL for an
+incoming BFD control packet.
+
+This feature serves the purpose of thightening the packet validation
+requirements to avoid receiving BFD control packets from other sessions.
+```
+
+### Enable BFD in BGP
+
+```{cfgcmd} set protocols bgp neighbor \<neighbor\> bfd
+
+Enable BFD on a single BGP neighbor
+```
+
+```{cfgcmd} set protocols bgp peer-group \<neighbor\> bfd
+
+Enable BFD on a BGP peer group
+```
+
+### Enable BFD in OSPF
+
+```{cfgcmd} set protocols ospf interface \<interface\> bfd
+
+   Enable BFD for OSPF on an interface
+
+```
+
+```{cfgcmd} set protocols ospfv3 interface \<interface\> bfd
+
+Enable BFD for OSPFv3 on an interface
+```
+
+### Enable BFD in ISIS
+
+```{cfgcmd} set protocols isis \<name\> interface \<interface\> bfd
+
+Enable BFD for ISIS on an interface
+
+```
+
+## Operational Commands
+
+```{opcmd} show bfd peers
+
+   Show all BFD peers
+
+   :::{code-block} none
+   BFD Peers:
+        peer 198.51.100.33 vrf default interface eth4.100
+                ID: 4182341893
+                Remote ID: 12678929647
+                Status: up
+                Uptime: 1 month(s), 16 hour(s), 29 minute(s), 38 second(s)
+                Diagnostics: ok
+                Remote diagnostics: ok
+                Local timers:
+                        Receive interval: 300ms
+                        Transmission interval: 300ms
+                        Echo transmission interval: 50ms
+                Remote timers:
+                        Receive interval: 300ms
+                        Transmission interval: 300ms
+                        Echo transmission interval: 0ms
+
+        peer 198.51.100.55 vrf default interface eth4.101
+                ID: 4618932327
+                Remote ID: 3312345688
+                Status: up
+                Uptime: 20 hour(s), 16 minute(s), 19 second(s)
+                Diagnostics: ok
+                Remote diagnostics: ok
+                Local timers:
+                        Receive interval: 300ms
+                        Transmission interval: 300ms
+                        Echo transmission interval: 50ms
+                Remote timers:
+                        Receive interval: 300ms
+                        Transmission interval: 300ms
+                        Echo transmission interval: 0ms
+   :::
+```
+
+## BFD Static Route Monitoring
+
+
+A monitored static route conditions the installation to the RIB on the BFD
+session running state: when BFD session is up the route is installed to RIB,
+but when the BFD session is down it is removed from the RIB.
+
+
+### Configuration
+
+```{cfgcmd} set protocols static route \<subnet\> next-hop \<address\> bfd profile \<profile\>
+
+Configure a static route for \<subnet\> using gateway \<address\>
+and use the gateway address as BFD peer destination address.
+```
+
+```{cfgcmd} set protocols static route \<subnet\> next-hop \<address\> bfd multi-hop source \<address\> profile \<profile\>
+
+Configure a static route for \<subnet\> using gateway \<address\>,
+use source address to indentify the peer when is multi-hop session
+and the gateway address as BFD peer destination address.
+```
+
+```{cfgcmd} set protocols static route6 \<subnet\> next-hop \<address\> bfd profile \<profile\>
+
+Configure a static route for \<subnet\> using gateway \<address\>
+and use the gateway address as BFD peer destination address.
+```
+
+```{cfgcmd} set protocols static route6 \<subnet\> next-hop \<address\> bfd multi-hop source \<address\> profile \<profile\>
+
+Configure a static route for \<subnet\> using gateway \<address\>,
+use source address to indentify the peer when is multi-hop session
+and the gateway address as BFD peer destination address.
+```
+
+(bfd-operational-commands)=
+
+## Operational Commands
+
+```{opcmd} show bfd static routes
+
+Showing BFD monitored static routes
+
+:::{code-block} none
+Showing BFD monitored static routes:
+
+  Next hops:
+    VRF default IPv4 Unicast:
+        10.10.13.3/32 peer 192.168.2.3 (status: installed)
+        172.16.10.3/32 peer 192.168.10.1 (status: uninstalled)
+
+    VRF default IPv4 Multicast:
+
+    VRF default IPv6 Unicast:
+:::
+```
\ No newline at end of file