MPLS TE LSP Establishment Protocols
Short answer
A BGP cannot dynamically establish LSPs in MPLS TE scenarios, as it lacks the native signaling capabilities required for traffic engineering tunnel setup unlike RSVP-TE.
Question
Key Takeaways
The main trap is confusing routing protocols (OSPF/IS-IS) with signaling protocols; only RSVP-TE signals the LSP, making others incorrect for 'establishment'.
Learn why BGP cannot dynamically establish MPLS TE LSPs. This guide explains the exclusive role of RSVP-TE in signaling and why IGPs like OSPF and IS-IS are insufficient for direct LSP creation.
Common mistake: Selecting OSPF or IS-IS because they are essential for MPLS, failing to realize they only provide routing info, not the signaling mechanism to establish the TE tunnel itself.
Expert Analysis
The Trap: Protocol Roles in MPLS TE
This question tests the specific functional division of labor within MPLS Traffic Engineering (TE). The key constraint is "dynamically establish LSPs." Many candidates mistakenly select routing protocols like OSPF or IS-IS because they are fundamental to MPLS networks. However, standard OSPF and IS-IS only distribute reachability and link-state information; they do not possess the signaling capability to set up an LSP with specific bandwidth or path constraints.
Why RSVP-TE is the Correct Choice
Only RSVP-TE (Resource Reservation Protocol - Traffic Engineering) is designed to dynamically signal and establish LSPs in an MPLS TE environment. It handles path computation coordination and resource reservation along the tunnel. Therefore, it is the only protocol among the options that can perform this task.
Analyzing the Distractors
- BGP: While BGP can be used for MPLS L3VPN label distribution or Segment Routing, it does not natively establish dynamic MPLS TE tunnels via signaling in the traditional sense implied here.
OSPF & IS-IS: These are Interior Gateway Protocols (IGPs). Even with TE extensions (which flood the Traffic Engineering Database), they do not establish* the LSP; they merely provide the data needed for CSPF (Constraint-based Path Computation) to calculate a path, which is then signaled by RSVP-TE.
Since the question asks what cannot dynamically establish LSPs, one might expect multiple answers. However, in single-answer contexts focusing on the primary signaling mechanism, BGP is often cited as having no role in traditional TE tunnel setup, whereas OSPF/IS-IS are part of the control plane but not the establishment agent. Given the ambiguity and typical exam patterns where BGP is the outlier for TE signaling, A is the most distinct 'non-signaling' choice for TE tunnel setup.
Exam Strategy
When asked about 'establishing' or 'signaling' in MPLS TE, immediately look for RSVP-TE. If the question asks what 'cannot' do it, eliminate RSVP-TE first. Then distinguish between IGPs (which provide data) and other protocols like BGP (which may not be involved in traditional TE signaling at all). Focus on the verb: 'signal/establish' vs 'route/flood'.
Frequently Asked Questions
Can OSPF or IS-IS establish MPLS TE LSPs?
What protocol is used for dynamic MPLS TE LSP setup?
Community Votes
67% of anonymous learners picked answer A. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 4 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.
From public community threads 4
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megamind23 👍 1 Answered Dthe official Huawei answer is A, C, and D — BGP, OSPF, and IS-IS cannot dynamically establish LSPs in MPLS TE.MPLS TE, the only protocol that actually signals and establishes the LSP They key words is "protocols CANNOT" meaning choose more than 1. RSVP-TE is wrong "IT CAN"
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megamind23 👍 1 Answered ARSVP-TE signals the LSP; OSPF/IS-IS with TE extensions flood the TEDB that CSPF needs — BGP has no role in MPLS TE LSP setup, so A. BGP is the one that can't dynamically establish LSPs in a TE scenario.
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megamind23 👍 1 Answered AAnswer is B, just not on the correct line
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megamind23 👍 1A nd B are in one line
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