Exchanging Label Bindings - Cisco ASR 9000 Series Configuration Manual

Overview of Label Distribution Protocol
Configuring LDP Discovery for Passive Targeted Hellos, on page 26
Configuring LDP Discovery for Targeted Hellos: Example, on page 53

Exchanging Label Bindings

LDP creates LSPs to perform the hop-by-hop path setup so that MPLS packets can be transferred between
the nodes on the MPLS network.
This figure illustrates the process of label binding exchange for setting up LSPs.
Figure 2: Setting Up Label Switched Paths
For a given network (10.0.0.0), hop-by-hop LSPs are set up between each of the adjacent routers (or, nodes)
and each node allocates a local label and passes it to its neighbor as a binding:
1 R4 allocates local label L4 for prefix 10.0.0.0 and advertises it to its neighbors (R3).
2 R3 allocates local label L3 for prefix 10.0.0.0 and advertises it to its neighbors (R1, R2, R4).
3 R1 allocates local label L1 for prefix 10.0.0.0 and advertises it to its neighbors (R2, R3).
4 R2 allocates local label L2 for prefix 10.0.0.0 and advertises it to its neighbors (R1, R3).
5 R1's label information base (LIB) keeps local and remote labels bindings from its neighbors.
6 R2's LIB keeps local and remote labels bindings from its neighbors.
7 R3's LIB keeps local and remote labels bindings from its neighbors.
8 R4's LIB keeps local and remote labels bindings from its neighbors.
Related Topics
Setting Up LDP Neighbors, on page 29
Configuring LDP Neighbors: Example, on page 54
Cisco ASR 9000 Series Aggregation Services Router MPLS Configuration Guide, Release 4.3.x
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Implementing MPLS Label Distribution Protocol
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