Exchange on Hyper-V

Can you ping from Exchnage server to other IPs.?
If yes you have to check VLAN settings.
Did you make any settings in NIC?
Try to revert the change that will be a quick solution for you.

revert your change, I assume you have a decent backout plan

What did you change in the first place?

Hi, I can ping the router. The person that changed the settings, is not available anymore. Must I check VLAN settings on server or on Hyper-V?

OK,

So was this malicious? Unless you can give us some sort of direction as to what has happened we're going to struggle to resolve it.

No, it's not malicious. I understood that he changed NAT on server. Also he changed something on the vEthernet Virtual Switch

"I understood that he changed NAT on server."
It's possible he changed the IP address of the Exchange server, which would break NAT at the router.  I'm guessing the Exchange server has a static IP address rather than DHCP.  

When you ping the Exchange server, are you pinging it by host name or by IP?  Does the latter work while the former fails?  I'll go further and guess that the DNS entry for the Exchange server is static as well, rather than dynamic, which would cause these symptoms.

I can only enter a static IP on the Exchange server. Which DNS should be used here?
By the way, when I ping the host, only IPv6 is responding.

First confirm you can locally connect to the exchange server.
From the server itself
From a workstation in the Ian
Once you have this confirmed as working, meaning not an issue on the VM itself.
Then the remaining part to confirm whether the changes you made impacted a change and resulted by the firewall directing traffic to the wrong destination.

On the Hyper-V Host in elevated PowerShell please post the results of the following into a CODE snippet:

Get-NetAdapter | Sort MacAddress
Get-NetLbfoTeam
Get-VMSwitch
Get-VMNetworkAdapter | FL

Select allOpen in new window

"I can only enter a static IP on the Exchange server. Which DNS should be used here?"
My question is, "Is the Exchange server configured to use the IP address you think it's supposed to use?"  If the Exchange server's IP address is wrong, NAT won't work properly at the router.

You can see the IP address by going into the settings for the network adapter, or by typing IPCONFIG /ALL from a command prompt.  It should match the IP address you have in DNS for your Exchange server.