350-601 Question #436: Real Exam Question with Answer & Explanation

Question

Which two features are used to allow a nondisruptive upgrade for the ISSU process? (Choose two.)

Options

• Aconnectivity management processor
• Bnonstop forwarding
• Cgraceful restart
• Dstateful switchover
• Eadvanced services license

Explanation

Nonstop Forwarding (NSF) and Stateful Switchover (SSO) are two critical features that work together to enable a nondisruptive In-Service Software Upgrade (ISSU) process on network devices.

Common mistakes.

• A. A connectivity management processor (CMP) provides out-of-band management access but does not directly contribute to the nondisruptive nature of ISSU.
• C. Graceful Restart (GR) is a mechanism that allows a routing protocol neighbor to continue forwarding traffic based on known routes even if the peer routing process restarts, but it relies on NSF and SSO for its functionality during an ISSU.
• E. An advanced services license might enable certain features, but it is not a direct technical feature that facilitates a nondisruptive ISSU process.

Concept tested. ISSU, Nonstop Forwarding (NSF), and Stateful Switchover (SSO).

Reference. https://www.cisco.com/c/en/us/td/docs/routers/asr9000/software/asr9k_r4-1/system_management/configuration/guide/sysmgmt_cg41asr9k/sm_issu.html

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