Virtualizing XenServer - No networking for nested VMs

Hi,

I'm trying to run XenServer5 as a guest inside ESXi5 and got issues with networking for nested VMs(run inside XenServer)

My setup is configured like this:

pESXi5 --> vXenServer5 --> vWin2k8

            |

            --> vWinDHCP

The vWin2k8 VM can get DHCP IP from vWinDHCP and can ping vXenServer5,

but can't ping vWinDHCP nor any other machine on the network.

On one hand it seems like vWin2k8 has layer 2 connectivit(DHCP), at least up to the pESXi5 vSwitch,

On the other hand ARP requests to vWinDHCP are not getting answered, and no any Layer 3 conectivity as well.

I tried setting the physical interface on vXenServer5 to promiscuous mode and it didn't help.

Do I need to modify anything on the vSwitch? Maybe on the nested guest?

Any advice would be greatly appreciated!