Refer to the exhibit. You are designing MPLS-TE for this network. The links form Perth to Sydney and from Perth to Adelaide share the same optical fiber in one given segment. Which feature should…

Question

Exhibit

Options

• AShared Risk Link Groups
• BMPLS-TE Path Protection
• CMPLS-TE auto-tunnel backup
• DMPLS-TE Link protection

• A
  72% (18)
• B
  16% (4)
• C
  8% (2)
• D
  4% (1)

Explanation

Shared Risk Link Groups (SRLGs) solve this exact problem by logically grouping links that share a common physical resource - in this case, the same optical fiber segment between Perth-Sydney and Perth-Adelaide. When MPLS-TE is aware of these groupings, it will not route a backup tunnel over any link belonging to the same SRLG as the primary, preventing both paths from failing simultaneously on a single fiber cut.

Why the distractors are wrong:

• B (Path Protection) pre-computes an end-to-end standby LSP, but without SRLG configuration, it has no awareness of shared physical infrastructure and may inadvertently select the same fiber for the backup path.
• C (Auto-tunnel Backup) automates FRR backup tunnel creation, but automation alone doesn't prevent the backup from traversing the same optical fiber - it needs SRLG information to constrain path selection.
• D (Link Protection) is an FRR mechanism that protects a single link hop-by-hop, but like the others, it doesn't inherently understand or avoid shared physical media without SRLG.

Memory tip: SRLG = "Same Risk, Link Group." When links share a risk (same fiber, same conduit, same duct), you group them so MPLS-TE treats them as a single point of failure and routes backups around the entire group.

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