Hi Victor,
Thank you for quick response. (and sorry for late response 
)
I will try to get Wireshark installed to get this corrected. Memory wise it is actually more than required. (24 GB). When I tried to ping DB (On which Repo is there) Server from existing 4.0 then I got 20 ms response. and when I do the same thing from other BO (3.1 Server) to DB Server I got the same 20 ms. So both are same. So I cannot prove if it really network.
My main question is, if if it network issue then it should be slow in using it. But after it starts it is just fine. No slowness. Why delay in start only?
I will install Wireshark and keep results ported?