View source for L2TP Tunneling

If you need to run a Layer 2 circuit over a Layer 3 network, you can set up an L2TP tunnel.  It can be applied to a variety of interfaces:
* VLAN interfaces on L3 switches, allowing it to provide access to all ports on a VLAN
* subinterfaces on routed interfaces on routers, allowing you to constrain it to a particular VLAN
* an entire routed interface on a router, allowing you to trunk VLANs through it.

==Configuration==
This needs to be applied to both ends of the connection.  The xconnect statement must point to the loopback interface on the remote router.
<PRE>
l2tp-class L2TP-TUNNEL
 hello 5
 password 7 110A1016141D
 cookie size 8
!
pseudowire-class L2TP-TUNNEL
 encapsulation l2tpv3
 ip local interface Loopback0
!
interface Loopback0
 ip address 172.16.5.2 255.255.255.255
!
interface Vlan1
 no ip address
 xconnect 172.16.5.1 1 encapsulation l2tpv3 pw-class L2TP-TUNNEL
</PRE>