Added internal interface mode

docs/source/interfaces.rst

@@ -1291,6 +1291,15 @@ the default mode.
      public Transport Node available on the Internet, the interface
      connecting over the Internet should be set to ``boundary`` mode.
 
+ * | The ``internal`` mode designates interfaces that belong to an
+     network different from any marked as ``boundary``. Announces from
+     a ``boundary`` interface will not propagate to interfaces set as
+     ``internal``, but announces *will* propagate from ``internal`` *to*
+     ``boundary``. Devices on the ``internal`` side of the network will
+     still be able to resolve paths to destinations across the boundary
+     when needed, since recursive path requests are enabled for ``internal``
+     mode interfaces by default.
+
 For a table describing the impact of all modes on announce propagation,
 please see the :ref:`Announce Propagation Rules<understanding-announcepropagation>` section.
 

docs/source/understanding.rst

@@ -714,23 +714,33 @@ See the :ref:`Interface Modes<interfaces-modes>` section for a conceptual overvi
 .. 
       (.. code-block:: text)
       Full ────── ✓ ──┐              ┌── ✓ ── Full
-      AP ──────── ✓ ──┼───> Full >───┼── ✕ ── AP
-      Boundary ── ✓ ──┤              ├── ✓ ── Boundary
+      AP ──────── ✓ ──┤              ├── ✕ ── AP
+      Boundary ── ✓ ──┼───> Full >───┼── ✓ ── Boundary
+      Internal ── ✓ ──┤              ├── ✓ ── Internal
       Roaming ─── ✓ ──┘              └── ✓ ── Roaming
 
       Full ────── ✕ ──┐              ┌── ✓ ── Full
-      AP ──────── ✕ ──┼────> AP >────┼── ✕ ── AP
-      Boundary ── ✕ ──┤              ├── ✓ ── Boundary
+      AP ──────── ✕ ──┤              ├── ✕ ── AP
+      Boundary ── ✕ ──┼────> AP >────┼── ✓ ── Boundary
+      Internal ── ✕ ──┤              ├── ✓ ── Internal
       Roaming ─── ✕ ──┘              └── ✓ ── Roaming
 
       Full ────── ✓ ──┐              ┌── ✓ ── Full
-      AP ──────── ✓ ──┼─> Roaming >──┼── ✕ ── AP
-      Boundary ── ✕ ──┤              ├── ✕ ── Boundary
+      AP ──────── ✓ ──┤              ├── ✕ ── AP
+      Boundary ── ✕ ──┼─> Roaming >──┼── ✕ ── Boundary
+      Internal ── ✕ ──┤              ├── ✕ ── Internal
       Roaming ─── ✕ ──┘              └── ✕ ── Roaming
 
       Full ────── ✓ ──┐              ┌── ✓ ── Full
-      AP ──────── ✓ ──┼─> Boundary >─┼── ✕ ── AP
-      Boundary ── ✓ ──┤              ├── ✓ ── Boundary
+      AP ──────── ✓ ──┤              ├── ✕ ── AP
+      Boundary ── ✓ ──┼─> Boundary >─┼── ✓ ── Boundary
+      Internal ── ✓ ──┤              ├── ✕ ── Internal
+      Roaming ─── ✕ ──┘              └── ✕ ── Roaming
+
+      Full ────── ✓ ──┐              ┌── ✓ ── Full
+      AP ──────── ✓ ──┤              ├── ✕ ── AP
+      Boundary ── ✕ ──┼─> Internal >─┼── ✓ ── Boundary
+      Internal ── ✓ ──┤              ├── ✓ ── Internal
       Roaming ─── ✕ ──┘              └── ✕ ── Roaming