Hi Ankush,
SIP Server itself can perform as a switch thus there is no need for a physical one. You question about minimum configuration required is a little vague to answer with any type of recommendation.
I would suggest review the Genesys SIP Server 8.1 Deployment Guide (
http://docs.genesys.com/Special:Repository/81fr_dep-sip.pdf?id=2e30d00a-05d6-4c84-a539-eb7ddcbde5f4) which has a Prerequisites section, and it also goes into detail on each option, configuration, etc. Each deployment/environment brings upon it's own required configurations.
Should you have specific questions with regards to issues you are seeing while deploying, I have found the Genesys Customer Care team to be more than helpful in assisting with issues yoy may encounter.
Cheers