LDP Session Protection and LDP IGP Sync: Exam 400-201 Cisco CCIE Service Provider Written Exam

LDP Session Protection and LDP IGP Sync


Which statement about LDP Session Protection and LDP IGP sync is true?



Click on the arrows to vote for the correct answer

A. B. C. D.


LDP (Label Distribution Protocol) is a signaling protocol used in MPLS (Multiprotocol Label Switching) networks to distribute labels and establish label-switched paths (LSPs) between routers. LDP Session Protection and LDP IGP sync are two LDP features that are used to improve network stability and convergence in the event of a link or node failure.

LDP Session Protection is a feature that helps maintain LDP session continuity in the event of a session failure. When LDP Session Protection is enabled, the router that detects a session failure sends a notification to its peer, and the peers initiate a label re-distribution process to restore the session. This helps to avoid the need for a complete re-establishment of the LDP session, which can be time-consuming and cause service disruption.

LDP IGP sync, on the other hand, is a feature that helps synchronize the LDP labels with the IGP (Interior Gateway Protocol) topology. This ensures that the labels are distributed in accordance with the IGP topology, which helps prevent label mismatches and packet drops. When LDP IGP sync is enabled, the LDP protocol exchanges label information only after the IGP protocol has converged. This ensures that label information is exchanged only on stable IGP topologies.

Based on the above explanation, option C is the correct answer. LDP Session Protection re-exchanges label information when a down-up event occurs, while LDP-IGP sync keeps the adjacency and label information in a down-up event. Both features can be used together to improve network stability and convergence in a MPLS LDP-enabled network. Option A is incorrect, as it implies that both features are required to increase fast convergence, while they are actually used to improve network stability. Option B is also incorrect, as both features can be used at the same time. Option D is incorrect, as it confuses the functions of the two features.