Copy advanced connectivity from Trellis-docs

Change-Id: I428eb80a4312570cc548a9804b3c0b17930a1cf7
diff --git a/advanced/connectivity.rst b/advanced/connectivity.rst
index 1221313..c9d1f01 100644
--- a/advanced/connectivity.rst
+++ b/advanced/connectivity.rst
@@ -1,2 +1,13 @@
 Advanced Connectivity
 =====================
+
+SD-Fabric supports DHCP relay, dual homing and external connectivity.
+
+.. toctree::
+   :maxdepth: 2
+   :hidden:
+   :glob:
+
+   connectivity/dhcp-relay
+   connectivity/external-connectivity
+   connectivity/dual-homing