MPLS tunnels are a way to represent an LSP to traditional routing protocols
or IP services in a way which the understand, as an interface.
MPLS tunnels are also one way or doing LSP heiearchy.

To create an MPLS tunnel manually:
-create an outgoing label

mplsadm -A -O gen:1024:eth1:ipv4:192.168.0.1

-create an mpls tunnel interface

mplsadm -A -T mpls0

-assign an IP address to the tunnel (it can be the same as the true
 interface it goes out, or maybe as a point-to-point with the IP address
 of the end of the LSP being used.

ifconfig mpls0 192.168.0.2 netmask 255.255.255.255

-bind the outgoing label to the tunnel

mplsadm -B -O gen:1024:eth1 -T mpls0

-add a route to forward traffic out mpls0

route add -net 172.16.0.0/16 mpls0

-any traffic to 17.16.0.0/16 now goes out eth1 with label 1024.


You can create an outgoing label on an MPLS tunnel interface:

-after the tunnel is setup as above, create an outgoing label on mpls0

mplsadm -A -O gen:2048:mpls0

-bind a FEC to it or create another tunnel interface on top of it

route add -net 172.16.1.0/24 mpls0
mplsadm -B -O gen:2048:mpls0 -f 172.16.1.0/24

    -or-

mplsadm -A -T mpls1
mplsadm -B -O gen:2048:mpls0 -T mpls1
route add -net 172.16.1.0/24 mpls1

-both options above produce the same affect, any traffic to 172.16.1.0/24
 leaved eth1 with the label stack 1024:2048 and any traffic to the less
 specific 172.16.0.0/16 goes out eth1 with the label 1024.