Refer to the exhibit. An engineer has configured an IP SLA for UDP echo's. Which command is needed to start the IP SLA to test every 30 seconds and continue until stopped?

The `ip sla schedule 100 start-time now life forever` command correctly schedules IP SLA operation 100 to begin immediately and continue running without a stop time, fulfilling the requirement to test every 30 seconds and continue until stopped.

The operation number 30 in this command does not match the implicitly specified operation 100 from the question context and the correct answer refers to operation 100.

The `life 30` parameter would cause the IP SLA operation to run for only 30 seconds, which contradicts the requirement for it to continue until stopped.

This command is missing the `start-time now` parameter, which is essential for the IP SLA operation to begin immediately as required.