Iteration Length

Iteration length in agile software development is the time between two consecutive customer feedbacks.

You can set up iteration length to 2 weeks in the JIRA, but if you meet your customer twice a year then your iteration length is 6 months. You can do iteration demo every 2 weeks, but if nobody except your manager sees the demo then your iteration length is not 2 weeks. You can even release some artifacts and change the version of your application every 2 weeks, but if your customer never tried to use your application then your iteration length is definitely not 2 weeks.

In general, without customer feedback there is no iteration. It's a cascade.