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+.. _interfaces-tunnel:
+
+Tunnel Interfaces
+=================
+
+Generic Routing Encapsulation (GRE)
+-----------------------------------
+
+A GRE tunnel requires a tunnel source (local-ip), a tunnel destination (remote-ip), 
+an encapsulation type (gre), and an address (ipv4/ipv6).  Below is a configuration example 
+taken from a VyOS router and a Cisco IOS router.
+
+**VyOS Router:**
+
+.. code-block:: sh
+
+  set interfaces tunnel tun100 address '10.0.0.1/30'
+  set interfaces tunnel tun100 encapsulation 'gre'
+  set interfaces tunnel tun100 local-ip '198.18.0.2'
+  set interfaces tunnel tun100 remote-ip '198.18.2.2'
+
+**Cisco IOS Router:**
+
+.. code-block:: sh
+
+  interface Tunnel100
+  ip address 10.0.0.2 255.255.255.252
+  tunnel source 198.18.2.2
+  tunnel destination 198.18.0.2
+
+The main difference between these two configurations is that VyOS requires you explicitly 
+configure your encapsulation type.  The Cisco router defaults to 'gre ip'.
+
+
+Virtual Tunnel Interface (VTI)
+------------------------------
+
+Set Virtual Tunnel Interface
+
+.. code-block:: sh
+
+  set interfaces vti vti0 address 192.168.2.249/30
+  set interfaces vti vti0 address 2001:db8:2::249/64
+
+Results in:
+
+.. code-block:: sh
+
+  vyos@vyos# show interfaces vti
+  vti vti0 {
+      address 192.168.2.249/30
+      address 2001:db8:2::249/64
+      description "Description"
+  }