Symantec Endpoint Firewall slows Hyper-V Virtual machines network throughput
I've recently been through some migrations for clients from physical machines to virtual machines. The speed difference without Symantec Endpoint firewall installed can nearly double the copy speeds. The antivirus doesn't seem to have any significant impact on speed. Using Windows native firewall works fine. It is only the Symantec Endpoint firewall that slows the network throughput significantly.
I've changed the offload on the nics and I've updated the nics - firmware/drivers.
I am using Windows Server 2012 R2 Datacenter with Windows Server 2012 R2 standard hyper V VMs. I'm using 12.1.4 of Endpoint.