Cisco Cisco IOS Software Release 12.0(22)S

Because AAL5  over MPLS does not support fragmentation and reassembly, ensure that the maximum 
transmission unit (MTU) of all intermediate links between endpoints is sufficient to carry the largest 
ATM AAL5 SDU received.

You must enable LDP label distribution for the dynamic MPLS tunnels used for AAL5  over MPLS.

See the following sections for configuration tasks to enable AAL5  over MPLS:

 (required)

 (optional)

 (required)

Make sure dynamic MPLS switching is enabled on all interfaces in your core, including traffic 
engineering tunnels.

To configure a dynamic MPLS tunnel to transport ATM SDUs between two endpoints, perform the 
following steps on the  routers that are endpoints of the tunnel.

The commands used to create an MPLS tunnel are supported only on Cisco IOS Releases 12.0(10)ST to 
12.0(21)ST. 

Router(config)# interface tunnel tunnel_number

Configures a tunnel interface and enters the interface 
configuration mode. Specify the number of the tunnel 
interface that you want to create and configure.

Router(config-if)# tunnel mode mpls dynamic

Sets the encapsulation mode for an MPLS tunnel on all 
interfaces in the core.

Router(config-if)# tunnel destination ip-address

Specifies the destination for the tunnel interface. We 
recommend that you use the loopback address as the 
tunnel destination address. Make sure the backbone 
network does not perform summarization of this 
destination address.  The IP address of the host 
destination is expressed in decimal in four-part, dotted 
notation.