Windows Server 2008 and above computers with the Hyper-V role installed may appear to lose network connectivity after the Network Threat Protection (NTP) component of the Symantec Endpoint Protection (SEP) client is installed to them, however, the virtual machines that are managed by Hyper-V are still able to communicate with each other across their virtual switch.
The following error may appear in the Windows System log:
Source = VMSMP
Error = Port 'SWITCHPORT-SM-CE41CD8E-A694-4EE3-947D-58D656B4181B-0-1' was prevented from using MAC address '00-15-5D-02-0A-01' because it is pinned to port '14497C9E-C392-446C-B'.
Event ID = 28