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.
This needs to be applied to both ends of the connection. The xconnect statement must point to the loopback interface on the remote router.
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