CCNP SP MPLS FAQ: Label Distribution Protocol

CCNP SP MPLS FAQ: Label Distribution Protocol

Q1. What is the fundamental purpose of LDP?

Answer: The fundamental purpose of LDP is to distribute label bindings.

Q2. Name the four main functions that LDP takes care of.

Answer: The four main functions that LDP takes care of include the following:
  • The discovery of LSRs that are running LDP
  • Session establishment and maintenance
  • Advertising of label mappings
  • Housekeeping by means of notification

Q3. How can you reduce the number of label bindings on an LSR?

Answer: To reduce the number of label bindings on an LSR, you can either control the advertisement of label bindings via LDP in the outbound direction, or you can filter the incoming label bindings.

Q4. What problem does MPLS LDP-IGP synchronization solve?

Answer: MPLS LDP-IGP synchronization solves the problem of labeled packets being dropped when the LDP information is out of sync with the IGP.

Q5. How many LDP sessions are established between two LSRs that have six links between them, of which two links are LC-ATM links and four are frame links?

Answer: Three LDP sessions are established in that case.

Q6. What do you need to configure to protect the LDP sessions against attacks?

Answer: You need MD5 authentication for the LDP neighbor.

Q7. What trick does MPLS LDP-IGP Synchronization employ to ensure that the link is not used to forward traffic while the LDP session is unsynchronized?

Answer: MPLS LDP-IGP Synchronization has the IGP advertise the link with the maximum metric.

Q8. What does LDP Session Protection use to protect an LDP session?

Figure: LDP Session Protection

ccnp-sp-mpls-faq-label-distribution-protocol

Answer: LDP Session Protection uses a targeted LDP session.

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