350-501 Question #25: Real Exam Question with Answer & Explanation

Question

Refer to the exhibit. Which effect of this configuration is true?

Options

• AR1 can support a peer that is configured for LDP SSO/NSF as the peer recovers from an outage
• BR1 can failover only to a peer that is configured for LDP SSO/NSF
• CR1 can failover to any peer
• DR1 can support a graceful restart operation on the peer, even if graceful restart is disabled on the

Explanation

When ldp graceful-restart is enabled, R1 can support non-stop forwarding (NSF) functionality, allowing it to maintain LSP forwarding when a peer recovers from an outage.

Common mistakes.

• B. LDP graceful restart allows R1 to support a peer undergoing NSF/SSO, but it does not restrict R1's failover capability only to such peers.
• C. LDP graceful restart is specific to maintaining LSPs during peer outages with NSF-capable peers and does not imply failover capability to any peer in a general sense, nor is it about routing protocol failover.
• D. The statement implies R1 can support a graceful restart on a peer even if graceful restart is disabled on R1, which is incorrect; both ends generally need to negotiate graceful restart capability for it to function effectively.

Concept tested. LDP graceful restart functionality

Reference. https://www.cisco.com/c/en/us/td/docs/ios/mpls/configuration/guide/12_4t/t_mpls_12_4t_book/t_mpls_mpls_ldp.html

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