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352-001 · Question #689
352-001 Question #689: Real Exam Question with Answer & Explanation
The correct answer is A: Deploy MPLS TE. MPLS Traffic Engineering with Fast Reroute provides pre-computed backup LSPs that enable near-instantaneous traffic rerouting around a failed P node without waiting for IGP reconvergence.
Question
A customer uses OSPF and BGP in their network. Which solution will continue forwarding packets during a temporary failure of a P node?
Options
- ADeploy MPLS TE
- BEnable BGP Flowspec
- CEnable NSF/GR for OSPF
- DDeploy IS-IS an IGP instead of OSPF
Explanation
MPLS Traffic Engineering with Fast Reroute provides pre-computed backup LSPs that enable near-instantaneous traffic rerouting around a failed P node without waiting for IGP reconvergence.
Common mistakes.
- B. BGP Flowspec distributes traffic filtering and steering policies via BGP UPDATE messages and is designed for DDoS mitigation and traffic policy - it does not provide pre-computed alternate paths to maintain forwarding through a failed P node.
- C. NSF/GR for OSPF preserves forwarding entries on a single device during a control plane restart or supervisor switchover, but it cannot maintain forwarding when a completely separate physical P node fails and is removed from the topology.
- D. Replacing OSPF with IS-IS changes only the routing protocol and does not add any fast-reroute or pre-computed backup path capability - both protocols have similar reconvergence times without additional TE mechanisms.
Concept tested. MPLS TE Fast Reroute node protection
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