Since I didn't find any need to connect to external network I haven't deployed router. For testing I have deployed a virtual router now to connect external network and my VM's on nested ESXi can connect to external network and was able to ping the DC VC etc..
1) Deploy a Virtual Router download from here http://freesco.sourceforge.net/
2) Connect two network to the router as show in the snap and configure the router
3) Configure all VM's Default Gateway (i.e DC VC and ESXi Host) to use router's IP.
4) Finally VM's on nested ESXi will be able connect external network and ping to other VM's too.