The CCNA is a prequisite for the CCNA-Voice.
You can complete the CCNA by either completing the single exam 640-802
Or by completing ICND 1 & 2.
Ok, I have this same question because if you look at the certification path page on Cisco's site they make it look like you can take the CCNA Voice or CCNA Wireless after only taking the CCENT ICND1 certiciation exam? Am I wrong in this view?
If you look at the CCNA-Voice Certification syllabus page.
It clearly states that the CCNA is a prerequisite of the CCNA Voice Certification. Therefore you need to complete one of the two paths to CCNA certification before you can be a certified CCNA-Voice.
You can take any of the tests that Cisco offers, but you will not gain the certification or title, unless you meet the pre-requisites, in this case, holding a current valid CCNA. So you would have to recertify to get the new certification.