A Hyper-v host (Windows server 2008 R2) is installed on Vmware ESXi 5.5. Another Windows server 2008 R2 is installed as a guest on Hyper-v. The problem is that the guest does not have access to the rest of the network accept for the host. The virtual switch has external type. In similar scenarios not involving nested virtualization with ESXi networking works without any issues. Is there anything to check on ESXi side?
I'm fairly certain that you need to enable (Accept) promiscuous mode on the ESXi virtual switch that's attached to your nested Hyper-V host (which is in turn attached to your Hyper-V virtual switch).