JN0-360 | Which two statements regarding the MPLS label…

Question 42:

Which two statements regarding the MPLS label information base are correct? (Choose two.)

A. The MPLS label information base is stored in the inet.3 table.
B. The MPLS label information base is stored in the mpls.0 table.
C. The label information base is used by all LSRs to forward LSP traffic.
D. The label information base is used by transit LSRs to forward LSP traffic.

Answer: B,D

Explanation:

Labels represent the FEC along the LSP from the ingress node to the egress node. The label is prepended to the packet when the packet is forwarded to the next hop. Each label is valid only between a pair of LSRs. A downstream LSR reached by a packet uses the label as an index into a table that contains both the next hop and a different label to prepend to the packet before forwarding. This table is usually referred to as a label information base (LIB).

LIB (Label Information Base) is the software table maintained by IP/MPLS capable routers to store the details of port and the corresponding MPLS router label to be popped/pushed on incoming/outgoing MPLS packets. Entries are populated from label-distribution protocols. LIB functions in the control plane of routers MPLS layer. It is used by the label distribution protocol for mapping the next hop labels.

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