I've got the same today right after 1709 updates.on win 10 64bits
No stright forward solutions.
I lost the connectivity on the guest and the host
To recover the connection on the host I had to:
Delete the vEthernet interface
Delete the Etherent interface.
For Hyper-V guest
Initialy No chance to recover,
Recreating the vSwitch did not help.
vSwicth was alwye coming back with status disconeted.
I finally noticed that the original Intel Ethernet driver was replaced by a MS 1709 ethernet adaptor version!.
I re-installed the Intel version and all strated to work like a charm.
Conclusion: MS Ethernet driver looks like ... pretty bad.
in my case:
Intel NIC: Intel(R) I219-LM
I used the driver 22.9 https://downloadcenter.intel.com/product/82185/Intel-Ethernet-Connection-I219-LM (Downloads for Intel® Ethernet Connection I219-LM )