Question

A service provider runs LDP across its core using default Cisco IOS behavior. A network engineer notices that during an IGP convergence event, some LSRs begin advertising a label mapping for a FEC to their upstream neighbors before the downstream label mapping for that same FEC has been received. This creates a brief window where an LSR advertises a label but has no valid downstream label to swap to. Which LDP label distribution control mode explains this behavior, and what is its key characteristic?

Accepted Answer

Independent label distribution control — each LSR advertises label mappings for a FEC independently, without waiting to receive a label from the downstream next hop.

Answer

Ordered label distribution control — an LSR advertises a label mapping only after it has received a label mapping from the downstream next hop (or is the egress) for that FEC.

Answer

Downstream-on-demand label advertisement — an LSR advertises labels only when explicitly requested by an upstream peer.

Answer

Conservative label retention — an LSR retains only the label mapping received from its current next-hop neighbor and discards all others.