Teamed NICs no longer work after upgrade to 2012 R2

Hi,

My Hyper-V installation on 2012 Data Centre used two teamed NICs as a Hyper-V virtual switch configured to connect to the external network.

After upgrading to 2012 R2 Data Centre I no longer have connectivity to the external network. VMs that use this switch no longer have network connectivity.

I've removed the switch and reconfigured but with no joy. I've also completely removed the Hyper-V role and reinstalled but again - no joy.

For the time being the NICs are configured as separate switches and all is OK.

Any ideas?

Many thanks,

Sean