350-401 Question #422: Real Exam Question with Answer & Explanation

Question

An engineer is concerned with the deployment of a new application that is sensitive to inter- packet delay variance. Which command configures the router to be the destination of jitter measurements?

Options

• ARouter(config)# ip sla responder udp-connect 172.29.139.134 5000
• BRouter(config)# ip sla responder tcp-connect 172.29.139.134 5000
• CRouter(config)# ip sla responder udp-echo 172.29.139.134 5000
• DRouter(config)# ip sla responder tcp-echo 172.29.139.134 5000

Explanation

Explanation

Option C is correct because jitter (inter-packet delay variance) is measured using UDP-based IP SLA operations, and the udp-echo responder type is specifically designed to receive and respond to UDP echo probes used for jitter testing - the IP address and port number define where the router listens as the destination. Option A (udp-connect) is incorrect because that operation type is used for testing UDP connectivity/reachability, not jitter measurement. Options B and D are wrong because TCP-based SLA operations cannot measure jitter - TCP's built-in retransmission and sequencing mechanisms make it unsuitable for delay variance testing, which requires the stateless, real-time nature of UDP. Option D (tcp-echo) would also be incorrect syntax for a responder command in most IOS versions.

Memory Tip: Think "Jitter = UDP Echo" - jitter measures timing between packets, and UDP is the only protocol that exposes raw timing without TCP's interference. If you see "jitter" on the exam, immediately associate it with udp-echo on both the source (SLA operation) and destination (responder).

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