CCIE Service Provider Written Exam: Ensuring Label Bindings Stability

Configuring MPLS and LDP for Link Redundancy

Question

Two routers that are running MPLS and LDP have multiple links that than connect them to each other.

An engineer wants to ensure that the label bindings are not flushed from the LIB if one of the links fails.

Which configuration meets this requirement?

Answers

Explanations

Click on the arrows to vote for the correct answer

A. B. C. D.

D.

The answer that meets the requirement of ensuring that the label bindings are not flushed from the Label Information Base (LIB) if one of the links fails is option C, the "mpls ldp sync" command under router process configuration mode.

Explanation:

MPLS and LDP are protocols used for forwarding packets in a network. When these protocols are used on multiple links that connect two routers, label bindings are created in the LIB of each router. These label bindings map network addresses to labels that are used for forwarding packets.

In case of a link failure, the label bindings that were associated with the failed link are removed from the LIB. This can result in the interruption of traffic flow.

To avoid this situation, the "mpls ldp sync" command can be used. This command enables the synchronization of label bindings between the two routers. When a label binding is created on one router, it is automatically propagated to the other router, ensuring that both routers have identical label bindings in their LIBs.

This synchronization feature ensures that if one of the links fails, the label bindings associated with the failed link are still available on the other router, allowing traffic to continue to flow. Therefore, the "mpls ldp sync" command is the best option to ensure that label bindings are not flushed from the LIB if one of the links fails.