Initial requirements:

You must be sponsored or employed by a Cisco Learning Partner (CLP) and pass the associated course and exam(s) for your chosen technology. You must then pass the Instructor Certification Process (two-day evaluation) and acknowledge the Cisco Certified Systems Instructor Agreement. After passing the Instructor certification process, your sponsor will submit and request certification on your behalf.

Continuing requirements: 
You must be an active CCSI. This requires maintaining affiliation with a Learning Partner in order to maintain your CCSI certification. If you are inactive for one year or longer, you will be required to recertify.