IF you already have sso 5.5 update1 or later than in that case no need of using the identity appliance.If lower than we have to download the identity appliance.
Kindly mark this as helpful/correct answer if this answer your query.
If you haven't already, check out stvkpln's comments on this thread vRA: Identity Appliance or vSphere SSO when there are multiple vCenters (each with their own SSO) in... he makes some good points worth considering when choosing between SSO and ID appliance. I use the ID appliance. It reduces dependencies and since AD is the real source of truth when it comes to authentication unified SSO doesn't provide much benefit. Another thing to consider is that with vSphere 6 it is recommended to have an external PSC if more than 1 vCenter or service will be part of the SSO domain. So either way you're looking at an additional machine. Personally, I'd rather deploy the the ID appliance and be done with it than deal with an external PSC with vCenter and vRA connected to it. Just my thoughts on the matter.
