Which Table to Look at for MPLS Network Forwarding Behavior Verification?

A.

When a packet enters an MPLS network, it is encapsulated with a label that identifies the path it should take through the network. The label forwarding information base (LFIB) is used to maintain the forwarding state for labeled packets at each Label Switching Router (LSR) in the MPLS network.

Therefore, to verify the forwarding behavior of an IP packet as it enters the MPLS network at the ingress LSR, the engineer should look at the LFIB. The LFIB is used to determine the outgoing interface and label that should be used to forward a labeled packet towards its destination.

The other tables mentioned in the answer choices are also important in the overall forwarding process in an MPLS network, but they are not directly related to the verification of forwarding behavior at the ingress LSR.

• The Label Information Base (LIB) is a table maintained at each LSR that maps incoming labels to outgoing labels. It is used to determine the label that should be attached to a packet as it is forwarded from one LSR to another.
• The Routing Information Base (RIB) is a table that stores the routing information learned from different routing protocols. It is used to determine the best path to reach a destination network.
• The Forwarding Information Base (FIB) is a table that is used to determine the forwarding path for IP packets based on the destination IP address. It is used to forward IP packets that are not labeled, such as packets that are entering or leaving the MPLS network.