What occurs when an MPLS packet is forwarded with no outgoing label (label pop/untagged)?
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Correct answer: Convert the incoming MPLS packet to an IP packet and forward it to the next router..
Why this is the answer
When an MPLS packet is forwarded with no outgoing label (label pop/untagged), it signifies the penultimate hop popping. This means the last label is removed, and the packet is converted back into its original IP packet format. The router then performs a standard IP lookup (FIB lookup) to determine the next hop based on the destination IP address. This process efficiently removes the MPLS overhead before the packet reaches its final destination, which may not be MPLS-aware. The option stating a RIB lookup is incorrect because forwarding decisions are made using the FIB (Forwarding Information Base), which is derived from the RIB (Routing Information Base) but optimized for fast lookup. Converting to an untagged packet and then a RIB lookup is also incorrect for the same reason. The last option is incorrect as it describes the opposite process of labeling, not unlabeling.
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