Hello Thomas,
in frame-based MPLS on interfaces using frames (PPP, ethernet, frame-relay, etc.) LDP per default uses per platform label space. This means, that the Label Forwarding Information Base (LFIB) will contain one label per destination network in the IP routing table. It does not matter on which MPLS enabled interface a labeled packet arrives - it will have the same label for a network.
In other words: with IP routing the FIB is used for every IP enabled interface. It does not matter on which interface an IP packet is received.
With label switching in frame-based MPLS the LFIB is used for every MPLS enabled interface. It does not matter on which interface a labeled packet is received.
Now there is a difference once you use cell-based MPLS. Here ATM cells respectively VPI/VCI are used for forwarding. The "label" is a VPI/VCI value. As in ATM VPI/VCI only have per interface significance, one needs a per interface label space (VPI/VCI). For a destination network the same label can - typically - not be used on different interfaces.
Per-platform label space is denoted by :0, whereas per interface label spaces are denoted by :1, :2, ...
The IP is the same in all cases and can be configured through "mpls ldp router-id [force]".
Hope this helps! Please rate all posts.
Regards, Martin
